I know Twitter is not government, and the first amendment doesn’t apply. Twitter is entirely within their rights to enforce their terms on their platform. I think this is probably a positive change. I’ve never encountered Loli material on Twitter, and I have no idea how much it’s used for that, but I have a general impression that very little of value will be lost from this change of policy.
However, I’m going to post Gaiman’s “icky speech” blog post anyways.