Uh probably because it's the right thing to do as so many feel it's appropriate to post their political and religious views here when its clearly not the right site for this stuff?
Probably because many of us don't want to be bombarded with other peoples agendas of promoting their politics into an audio gear related forum.
And no, they shouldn't have the "right" to post anything they want anywhere they want just because they're used to posting all over the web all day.