"Just report them afterwards" is not satisfactory when it comes to dealing with asshats
Riot, you can disagree with me on this, but I do not find reporting someone to be at all adequate when it comes to getting paired up with a pure asshat player. Very few of them give any f#cks about getting banned when they'll just make smurfs, and before a match ends, they do their damndest to ensure you go through hell. Try to fight back in any way? Riot punishes you for defending your pride and/or self-esteem, or for telling someone to go F*** themselves when they tell you to kill yourself.
Call me a hypocrite, call me as bad as them, I don't care. There are times when I seriously want to watch one of those asshats burned alive. And no amount of reporting or banning that guy is going to make that go away.
Surely you have to know how that feels.