Trolling in game.

Ok, i have noticed recently, that trolling in games has increased dramatically, even within the past couple months. When i first began playing, i believe was around the beginning of Season 6, (i know, i havent played for a long time) i could go into a game and not have to worry about anyone trolling or being annoying, game after game. but now, its nearly every time i play a game theres a troll or someone who wont do what they are supposed to. Example: I was in champ select and i called Jungle, nobody else had called jungle, only top, mid and support. So, while i was changing my spells, someone picked the champ i was going to play and they took smite, so i said, "hey, i got jungle" and their reply was "you got these nuts" so i just said whatever and went ashe adc, then as the last 2 seconds before the game started came, this person changed smite for ignite and there was nothing we could do about it. we got into game and the Yi started flaming me in /all chat. Myself and the rest of the team all knew he did wrong but there was nothing we could do, he than begun to feed the enemy adc causing me and my support to loose lane and ultimately loose the game. Granted, this was a blind match but, things like this have happened in some of the ranked games i have played, which is why i dont play ranked much either. Why do people do this? Is it for fun? to make everyone else miserable? odds are nobody will ever truly know, but all i can say is "Stop trying to ruin a game for everyone else, you might think its fun to follow someone around all game, steal their cs, get them killed, so on and so on" just play the game, and if your having a bad game, so what? dont ruin it for everyone else.