I'd hate to see that happen as a hard and fast rule. When you think about it, both politics and religion are built from ideas and ideals which, individually, should be easy enough to discuss. When these get lumped into a "system" that takes on a label that, in turn gets associated with a person or party, that's where trouble begins. If we could take out the labels and associations and deal with the specific ideas and ideals, it should work ok. Your mention of "some posters" is key. The topics aren't the guilty parties. I'd think that restrictions rather than total bans might be workable....or at least worth trying.