For that matter trolling isn't always a bad thing*; it can be a way to prove a good point if done well (see MannyGoldstein's alter-ego, "Third Way Manny" as an exceptional example of using the technique of trolling to make very good points).

There are trolls here, who make both pro- and anti-Obama posts. There are trolls who do so in a very thought-provoking way, and trolls who do so in incredibly tiresome and predictable ways. I don't think you need to imagine a conspiracy behind it; people just enjoy riling other people up online.

* NB: I'm using an older sense of "troll" from the Usenet days; it doesn't come from the creature that lives under a bridge and eats goats, but from the verb meaning "to fish". The original phrase was "trolling for newbies", and people would make shocking statements to get the inevitable reaction. In these latter days it has come to simply mean screaming misogynistic and anti-semitic epithets at people, but it's a much older and prouder tradition than that.