Sure, there are plenty of polite ... well mannered Obama supporters. Of that I have absolutely no doubt. Most of my coworkers are Obama supporters and they are all decent folks.
HOWEVER, most of the vandalism occurs from the leftists. I don’t think anyone can dispute that. This has nothing to do with Obama, but is a leftist problem. Look at the election in ‘04. Lots of lawn signs removed, cars being keyed, etc...
In this election, if racial tensions are stirred up in the case of an Obama loss (thanks to the professional race agitators) — it is not outside the possibility that there could be riots. I was a teen during the LA Riots thanks to Rodney King, and that is seared, seared into my memory.
I don’t think that McCain supporters of any race are going to riot if there is a McCain loss.
Most petty vandalism of all kinds is committed by teenagers and young adults. Political vandalism seems to be more often from the left, perhaps on account of the leftist message that “you’re oppressed so it’s okay to break the oppressor’s rules” and the leftist strategy of targeting youth who are quicker to buy into naive idealism). But totally pointless vandalism-for-kicks (e.g. egging cars, toilet-papering trees, keying nice cars that have no bumper stickers, etc.) doesn’t seem to have any political skew as far as I can tell.