Basically I think banning someone for the content of their proposals or implied proposals should be limited to the kind of the thing which might be banned by law (basically imminent threat of harm.)

LW self regulates the content of proposals via karma voting. In advancedatheist the communities desires were quite clearly expressed via karma votes and he still continued to bring up the topic.

Those post significantly reduce the likelihood that woman who read LW want to contribute. When the community karma votes that it doesn't want posts like this a user should accept that.