Any Web 2.0 system's basic premise is that it provides a space where humans can be humans. The bedrock assumption is that people can POST things that a server will instantly and automatically display publicly, and that the server owner will not instantly become legally liable for what they post.

This mirrors pretty well how the rest of the world operates. If I walk into a Macy's and start screaming libel or inciting a riot, the Macy's Corporation is not liable for that speech. Why should a 'digital property' like a social media site work differently?

Of course, it doesn't totally erase the server owner's liability. If someone posts child pornography that my server displays, it is my responsibility to remove it as soon as I become aware of it, just as it is Macy's responsibility to escort the libel-screamer off the premises. Failure to do that can confer liability onto me.

To break this consensus is to break the ability to foster human interactions on the internet that mirror how humans interact in the real world.