Conservative Christianity practices the chief sin of being "right." It may be a subset of pride, but it is "rightness" and "certainty" that is worshipped.
One of my favorite Christian philosophers, Soren Kierkegaard, put it this way:
The Bible is very easy to understand. But we Christians are a bunch of scheming swindlers. We pretend to be unable to understand it because we know very well that the minute we understand we are obliged to act accordingly.
For ultra conservative Christians the gospel is about having the right information--hence you get fundamentalists--and being "right" is everything. But if the gospel is about transformation--which I know it is---then being Christ like is everything.
Christian fundamentalists honestly believe having the right information about God is essential for salvation. For them, the greatest heresy would be to believe the wrong things about God. This is also why they can't bear to be around others who hold different beliefs than they do. If having the right information is what the Christian faith is all about, then having wrong information becomes the worst sin of all.
Mark Van Steenwyck, founder of the Mennonite Worker organization once wrote:
We have millions and millions of Christians who have had no experience of God, and the Church, for most part, prefers it that way. We can then supply beliefs and dogmas as a replacement for encountering a living God. This is part of the reason so many people cling to the Bible or their theological beliefs so firmly. Because, to them, it is the closest thing to God they have ever encountered.
But I met Jesus. I've tried to run from Him, prayed for Him to leave me be and let me burn in hell, but once Jesus gets a hold of a person because they once surrendered their life to Him, He will not let go.
Now I came out of that muddy mess that fundamentalism is. I was once there myself with all the "right" ideas about God and the Bible. Yet morality grows or it dies. It grew within me and that "faith" such as it was, was nothing more than the husk of an ugly caterpillar from which a butterfly would emerge (and continues to emerge decades later).
I'm not right about a lot of things, and my views have grown and changed and have been refined. But I do recognize when someone is living up to Christ's standard of us loving others like He loves us. There is no will within the vast majority of conservative Christians to live what they read--instead they want to preach about the sins of others (rather than repent for the ones they have) and they want to insist they are certain about EVERY thing.
I'm certain about little except that God loves me much more than I deserve, all my other beliefs about sin or righteousness mean nothing beside that relationship with Jesus. Seems to me that if one's relationship with God is not the primary spiritual goal, no matter how "right" or "certain" someone is, they have allowed themselves to become the Angel in the Garden of Eden passing commentary on what sins are the "biggest." -Wardendresden-