But if they don't smugly put you down, what will they have to think about later when they're touching themselves?
Seriously... I think it's shitty too. But if you expect the GIFT theory to ever change, you're kidding yourself. People are just assholes man. That 16 year old who's plat friend carried him is GONNA spam his mastery all game and put "GG EZ" at the end. If you get mad about it, you're just giving him what he wants... your rage and your attention.
Just ignore the idiot and realize that anyone who gets their jollies preening and posturing in a videogame isn't worth wasting the time to even respond to. Just go on to your next game and if you're upset about the fact that that player's douchebaggery isn't punished... remember that this is league we're talking about. The borked matchmaking will eventually put him against someone else JUST as rude, immature and obnoxious as he is who will stomp his nuts into the ground and BM him about it. Unless you're fighting some insane pro-level challenger player who never loses his games... that dumb kid is gonna get his face ripped off sooner or later by someone better/cheaper/more overpowered than him who will spill the same rudeness he thinks is cute to give others ALL over him. And he'll rage too...
So don't get upset by dumbasses and their smugness or their lack of basic human decency. Laugh at them. Because when the game does what it does best and shoves it's fist into their backside with a feeding bot lane or a camping jungler or something... they'll deserve it. It's not like any of this matters anyways... it's a freaking game. No sense getting mad over it, or over the little pecker who's preening because he happened to win one of the thousands and thousands and thousands of matches he'll play in his life.