MOBAs generate bad feelings because of the way numbers, teamplay, and win mechanics interact, in my opinion. That is to say, if there's a really crappy player on our team in TF2, then we just don't benefit very much from him. If our sniper doesn't sniper as many enemies as he might, then I just have more enemies at higher HPs then they would be if he'd shot them. As often as not, it won't make a difference to my gameplay experience.
But in Dota/LoL, if that sniper messes up, the other team gets kills, and now they're bigger. A fed character is much harder to kill than a normal one. A bad TF2 medic doesn't heal. A bad LoL medic overheals the other team.
As such, as the other team becomes more and more numerically entrenched in victory, turnarounds become increasingly impossible, but the game doesn't actually end for another 20 minutes, giving you 20 minutes to silently despise your former friends.