As a counter--perhaps we can do what Facebook WON'T do...
Have a "Dislike" button or, if you will, a "-1" to go with the "+1s," and at a certain "-X," you are then blocked from commenting on the thread?
That'd remove the monopoly over speech that having the thread starter control it all would have, as multiple -1s would have to come from multiple people (since we can only all +1 a comment once as it is, so same principle) and thus, say, once someone gets to -5 or -7 or whatever number it is, CLEARLY they're just dragging down the conversation, as there's enough here that, generally, a +1/-1 along party lines would break about even, and so even if you got a few -1s just for being a Democrat/Republican or theist/atheist, it still wouldn't be enough to push you ever the threshold...
It'd take BOTH SIDES and thus the MAJORITY giving you -1s to get to a -5 or -7 or -10 or whatever, and THEN it seems fair to "kick" someone from the discussion...at that point, they're clearly just flaming the thread, and both sides agree to that...