Ok, so I'm looking back through the thread to see what is going on.
If I'm correct, the proof of the demons over the internet (Demons over Internet Protocol as I would call them) is the potentially objectionable content (such as pornography) that exists online. In order for someone to see the proof, they would have to disable the blockers such as Google's Safe Search or something like Parental Filters on most browsers. The blockers you are talking about are like Parental Filters and Safe Search.
However...
This isn't correct.
If you're talking about the Supreme Court case with browser blockers, that was about public libraries and public schools. The Supreme Court rules in
United States v. American Library Ass'n that Congress has the authority to require public schools and require public schools and library receiving federal funds related to internet access to install filtering devices to prevent children from seeing obscene or pornographic images as per the Children's Online Protection Act.
https://en.wikipedia.org/wiki/United_States_v._American_Library_Ass'n#Conclusion
A browser is not required to come with filtering software, most websites will pornography or otherwise adult content will ask if you are over 18 before letting you visit however. This is to limit legal liability to the owner of the site. If a minor went on the site and did say 'yes', the owner would not be liable as they did make a reasonable effort to block a minor from entering the site, and the minor lied about their age/the parents were not supervising the minor's browsing. Similarly, Google enables safe-search automatically, to give themselves limited liability as it must be disabled and the button to disabled has a warning it might result in viewing adult content.
China meanwhile has censors in place to block quite a lot of things, such as information about The Tienanmen Square Riots and other political dissent. However, this involves things like preventing IP addresses from being routed through to the censored site using the servers the browser is attempting to hop through to reach it's goal. Almost all of the censoring is not browser-based, rather it is server based, and thus in greater control by the government as it cannot be edited on the user's machine. The ways of getting around this are a bit more difficult than simply using a different browser. This would involve using proxy servers and using a VPN or SSH to a computer outside of China. The government there has been trying to crack down on this and has blocked many of the free or popular VPN services have been blocked.
So no, it is not
required by law in the United States for browsers to filter out content. The closest thing to what you state is that sites with potentially dangerous to minors material must make a reasonable effort to prevent minors from accessing it.
I still would like a bit of clarification on the contradictions you presented. You first stated:
You said it was required by the government to filter.
You then said that it was up to the parents:
You then said that the Supreme Court was openly allowing pornography into the hands of minors.
How do you reconcile the contradiction between:
"Blocking objectionable material is required by the Supreme Court"
and
"The Supreme Court has struck down laws that blocked objectionable material from minors"