My personal opinion (ie not official moderation policy) is that political threads are allowed to remain active completely at the discretion and pleasure of the moderators, and that no one has any right to complain when they're closed down. That said -
wouldn't it have been better to warn or eject those involved since the majority of contributors in the thread were well behaved?
I don't know what thread YOU were reading, but the thread I was reading was garbage. "Well behaved"? I prefer "not technically against the rules". Besides, even if the discussion was still active, nobody in there has said anything vaguely intelligent in some time, it's just been childish sniping back and forth.