How about making paid servers ?
Have You ever considered such an option to make paid servers where player would have to pay 5$ or 10$ monthly for access. Just to get rid of those awful players since parents wouldnt pay 10$ monthly for some game. You know the easy way to sort out player population from those who care about winning and those who not since they have already paid for access so they would care ( at least in theory, trolls are everywhere ).