Why a good part of players in this game have so crap attitude?

More than 20% of the games I met people who ban my champion or to other teammate. It's really need an IQ test before to login to this game, who pass it can play, who don't pass it, it should not play. I mean, is cool 1 - 2 times someone didn't see what you want to play, but in my last games every time I met this kind of people? I suppose to have respect for this kind of people, but how I can give respect to someone who does not respect me?