Blizzard's automated system will ban you if you're reported by a team of jerks even if you're being scapegoated and dogpiled by the whole team and just standing up for yourself. Certainly not the first time it happens, but over a longer timeline.
The thing is, the vast majority of players of these games are teenagers who have no problem doing things like this if they feel bad about not winning.
And if it happens enough times you get a permanent ban which means to play again you need a new account which means you lost all your skins, which I'm sure is just fine with Blizzard.
So as a side effect tons of people don't use voice chat anymore, or have to selectively choose when they play or who they play with.
And that's not even counting the poor matchmaking which very often creates lopsided matches.
I can't understand why anyone would want to play these games once they go through some of these things enough times, but I suppose if you already have a group of friends you play these games with frequently, then you're largely immune to and naturally will never experience things like this.