Here's some trends I've noticed. Every time some politically-charged issue springs up, certain predictable actions seem to bog down debate:
1) Pointing out typos in the article summary or parent poster
Especially when the respondent makes their own typos while picking apart the OP. The flurry of people jumping on board to correct this can be enormous, and push valuable discussion down below the screen, where it has little chance of being seen.
2) Revising someone's analogy
Someone makes an analogy, so someone *else* has to make a better one. If the revised analogy is flawed, again the flurry of people jumping on board to correct this can be enormous and push valuable discussion down the page.
(Maybe when someone makes a bad analogy we should just say "no, it's not like that" and let it go?)
2) Saying it's our fault
I really hate this one. Invariably, someone will come along and say "it's our own fault because we voted for these people". This completely exonerates the politicians involved and makes everyone feel a little bit guilty - and at the same time it defuses calls for action, suggestions for improvement, and the like. "The best way is to use the power of the vote", setting aside that a) much of the time it's an unelected bureaucrat, b) the vote has been hijacked by special interests, and c) even if it were true, we should also be discussion other possible options.