Suffice to say a redraft which means that you'll have to go to court to determine what types of content you are and aren't allowed to moderate without the side effect of becoming responsible for everything people say on your web property is not an improvement.

What does that mean? Off-topic discussion does not fall outside of the 1st Amendment, and a restriction of the 1st Amendment to try and classify that as somehow less deserving of protection -- that would be a much greater curtailment of 1st Amendment rights than anything Facebook has done.

Bluntly, "would need to be litigated to find out" isn't an acceptable answer given that the people giving this answer are the same people proposing the legislation.

Courts don't decide what the law is, they interpret it. You have to have an idea of what you want the law to be, you can't kick that off to the courts. They're trying to interpret your intention and the letter of the law you propose, not the other way around.