Yeah I'm the same with WoW - in the 8 years I've been playing I've ran into far less douches than is the norm seemingly. Of course with any large game there's a chance of meeting people who are up to no good but I've generally found everyone to be very friendly. If someone kicks off it usually only takes someone to say something reasonable and not rise to it and it usually fizzles out pretty quickly.
Then again with the much play experience I also have a lot of knowledge about the game too and can firmly put people in their place (particularly the ones who mouth off about DPS etc)
Apart from LFR and AV - large groups like that arseholes seem a dime a dozen.
But anyway back on topic - just played another really close game of LoL that got very tense and frustrating in places but neither side resorted to trash talking and in the post-match lobby everyone was like that was awesome - thanks for the match!