Back in the day, when we were kids, the way you stopped douche baggery was putting the controller down and beating the shit out of one another. People tended to behave when the threat of actually getting their ass kicked was there to keep them in check.
As far as online gaming, there's nothing to stop it. It's a part of the beast.
I know Gran Turismo Sports online mode was similar, where the races and it's professionalism was entirely dependent on the players in the session. How did that ever pan out? I never ended up buying GT Sport.