There have already been explicit bans on topics. In the early days of Less Wrong, there were bans on discussing the Singularity and artificial intelligence, for fear that without such a ban the conversations about these topics would overwhelm the fledgling site and create an undesireable skewed tone. The ban was lifted after a certain amount of time, when the tone was supposedly established.

If pickup artist discussion is creating a tone that is skewed in ways we don't like, it is not without precedent and not in opposition to rationality to end it.