I've noticed that my atheist and agnostic liberal friends are hostile toward Christianity, but totally sympathetic to Islam, and I'm baffled as to why. It's to the point where they absolutely will become angry with you, accuse you of "racism," and declare that you are "misrepresenting" Islam when you criticize it. My best guess is that liberals with latch onto, make allies with, and defend anyone whom they view as oppressed.
I spent a great deal of time learning about Islam earnestly and open-mindedly while exploring religion. I spent considerable time at a mosque over the course of about 6 months, praying with them, chatting with numerous Muslims, reading the Quran front to back more than once, and studying the Hadith (teachings and sayings of Muhammad). Here is what I learned:
First, the positives. Muslims believe in freedom of religion; religion is not compulsory. Any Muslim society that follows the Quran and Hadith truly will allow Christians and Jews to practice freely. Also, they abhor racism. To Muslims, race does not matter. Mosques are multi-ethnic, and all Muslims are brothers and sisters. Racism is viewed as hatred of Allah's creation, which is a great sin. Of course, racism will still seep into some Muslim circles, as it does with every religion and even no religion. But the general view is anti-racist. These two things are where liberalism and Islam agree, and after this, there are no similarities whatsoever.
Now, a few points of contention.
The Islamic perspective is almost completely antithetical to secular and Christian liberalism. Moderate Islam is more extreme than even the most conservative brand of fundamentalist Christianity. On many social and religious issues, Islam is about 8 centuries behind the secular world, and that's not an exaggeration.
Part of accepting Islam is accepting Sharia in it's entirety, literally interpreted, with minimal changes to adapt to modernism. Sharia is Islamic religious law and government. This is true of ALL muslims, and I say this from my own experience. Ask any one of them if they accept Sharia, and they will tell you yes. No exceptions. This isn't a misconception at all. Sharia is laid out in the Quran and Hadiths of the prophet extensively, and the Quran teaches explicitly to obey the teachings of the prophet. The Quran and the Hadith lay out a blueprint for Islamic rule, and command that it be established and followed. This command is taken very seriously.
The liberal support of Islam is NOT reciprocated, generally. The Islamic world has a very low view of secular liberalism, and often identifies with conservatism, in spite of harsh criticism from Western conservatives. From the Islamic perspective, secular law leaves God out of governance, and disobeys His laws and governmental system as laid out explicitly in the Quran and Hadith. This is seen as a great evil. If you don't believe me, go to a mosque and ask them how they feel about secularism and Sharia.
Punishment for apostasy is death. This is clear and unambiguous in the Quran and Hadith. Read it for yourself if you don't believe me. Views on homosexuality are more extreme than the religious right in the US. It is a grave sin, on par with murder, and can be punished by death. The best you can hope for if you are caught in homosexual acts under Sharia is a beating, and this is in more moderate Muslim circles.
This is just the tip of the iceberg. Believe me, there is much, much more. And lest I am accused of misrepresenting, pick up any translation of the Quran and see for yourself. Talk to the Muslim community and see for yourself. Look up the Hadiths and see for yourself. It's all right there, clear as day. After learning about Islam to the extent that I have, and seeing that most of the criticisms of it are true, I cannot bring myself to support or defend it. Frankly, I'd rather live under a Pat Robertson dictatorship than any form of Islamic law.
EDIT: When I bring these things up to my liberal friends, they point to passages of the Bible that condone some of the same things. I'll address this point right now: Christianity and Judaism have both adapted to the modern world. For the most part, Islam has not.
As a liberal, I don't think that liberals generally defend "Islam". I think that is the way conservatives and all their propaganda outlets paint the picture. I think what liberals do is stick up for those who are oppressed on the basis of things like religion (and sex, age, race, etc.). When liberals defend muslims they are doing that - defending people who belong to a religion and are being persecuted for being members of that religion. They are not making any statement on the religion itself. Indeed, most liberals probably abhor what they perceive the religion of Islam to be, but they still will be protective of people to practice that religion and not be persecuted for it.
As for your assertion that atheists and agnostics defend Islam, I don't see that ever. At best, the liberal ones will defend the people of that religion but not the religion itself. Most atheists and agnostics in my experience are hateful towards the religion of Islam more than they hate Christianity or Judaism or just about any other religion. Bill Maher is a perfect example of the typical atheist that hates Islam (and yet will sometimes defend the people of that religion). So I can't relate or agree with your assertion that there are all these atheists/agnostics who defend Islam - I simply never, ever see that and I know many atheists and agnostics.
I find this entire thread interesting because people seem to have misunderstanding of Islam and Muslims across the spectrum. Conservatives and liberals have gross misunderstandings and the result is unusual and unfair reactions towards muslims. Even the "liberals" here, including yourself, have a very myopic view of muslims. It's probably because most here are very western and don't understand middle eastern cultures.
Being of a middle eastern background and having my ethnic history extremely influenced by Islam for centuries I don't share the same view as other westerners. I know what my family's and by extension my fellow Armenians' history is and that Islam is not a monolithic religion with a single and central authority from which orders are carried out.
My family and millions of Armenians were killed by the Muslim Turks. They were given the option to convert to Islam in order to live. Centuries before, the Persians did the same to Armenians. I know also that if not for the majority-Muslim nation of Syria my family and the vast majority of Armenians in the western world would not exist today. I know that my family spread to nations like Jordan (a Muslim country) where they were taken care of and treated well despite being Christians and they flourished. My mother's uncle, a genocide survivor, became King Hussein of Jordan's Royal Tailor. Islam is oppressive? We are a "dhimmi"? In Turkey we were a "dhimmi" but not in Jordan. But ignorant westerners throw that word around as if they know what they are talking about when in fact they don't.
Syria, Lebanon, Jordan, Iraq, Egypt, and even Iran showed far more hospitality and mercy to Christian Armenians than any Western nation ever did. They certainly showed us more hospitality and fair treatment than we Americans have ever shown them, especially these last decades when we destroy them and take no responsibility whatsoever (all the while we claim to be the "good" guys).
So this whole thread is funny to me. Funny as in strange. Funny in that people are making assertions about Islam and Muslims despite having never lived among them and experienced them and their cultures (which are diverse and varied) yet ignoring (for whatever reason) the goodness many muslim people, governments, nations, etc. have shown to Christians. There are Christians in many of the muslim-majority nations and often are treated extremely well and protected (Syria is one such example, Jordan another). People ignore this or they are simply ignorant about it.
My immediate and close extended family came mostly from Beirut, Lebanon. Both my parents and all their siblings born and raised there. If you asked any of them - ANY - how they feel about Muslims you would hear really great things. In fact, I'd say all of them felt more trusting of their Muslim neighbors than of their Christian non-Armenian neighbors. That's a sad statement on Christian unity but certainly an endorsement on the Muslim people and their morality in treating Christian neighbors.
Yes, there are radical Muslims nowadays and ones who hate Christianity and who want to harm Christians. There were the same before - the Turks are a great example of a nation that hates Christians with a passion for all of the centuries they existed right up until today. Ironically, the same Westerners (Americans especially) who like to spread anti-Muslim fear and hate are the very same who are best friends with the Turks and Saudis, two of the most virulent anti-Christian Muslim nations in the entire world, both of them worse than Iran when it comes to that.
But that's the whole point - hatred of Islam and Muslims is based purely in politics and that's why liberals will politically oppose at least the humanitarian side of things in which the rights of a muslim person are taken away when that person becomes oppressed and persecuted simply for being in that religion, no matter how much the liberal defending them may hate the religion itself.