Well, for one thing, this election may seem divisive from the perspective of Y!A, but on the internet anonymity makes everyone an ***hole.
In the real world, I think, this election may be a lot less divisive than the two that preceded it. The people who protested the political parties' conventions had specific issues and grievances, whereas in the past protests were geared to questioning the parties' right to exist at all.
There are far fewer people who think very poorly of John McCain or Barack Obama than for Gore and Bush in 2000, and fewer liberals have made their annual pledge to flee the country if their guy doesn't get elected.
In fact, it's quite hard to remember now what a polarizing figure Bush was in 2000 and again in 2004. Even on the Republican side, there were a lot of people that absolutely HATED him, and there were a lot of people that could not get excited about Gore, so you got a low turnout and a close election that could have been decided either way depending on whose rules you followed. In the past, there have been even more divisive elections, such as 1860 where the country actually split over the eventual winner, and the 19th century practice of burning your opponent if effigy has totally died out.
That's not to say this election isn't empassioning. What's true is that both candidates have done an excellent job getting people excited about them and their message, and while that leads to some pretty heated debates when the subject comes up, even the occasional accusation of racism doesn't disrupt the fabric of daily life that much. Usually it goes MUCH further than name calling.