The problem is this. The probability that politics is going to lead to unpleasantness is *very* high, given previous incidents across the network. If we do as you say and "lay in wait" until people get to the point where they are violating the Be Nice policy, the damage has already been done: Insults have been slung, feelings hurt and the chat conversation disrupted. What *benefit* is there to allow that to happen in the middle of the main chat room if we can contain it in dedicated rooms?
And if it doesn't happen, no harm has been done either, and the conversation continues happily in that…