Why are so many players passive aggressive, especially in more casual modes like aram and urf?

I've been taking a bit of a break from league lately since it's preseason, but almost all of my games have had players who are passive aggressive or just plain assholes in it. I'm not even talking about ranked either, i'm talking about normal games and ARAM games. "GG this bot", "JG diff", "my carries don't do any damage", *pinging a summoner spell cd/ult cd then typing "?"* , "trash x", "hit a x", etc. And it's not like the people who are on the receiving end of this are doing extremely poorly, normally they just made one minor mistake and get blasted for it for the rest of the game. It makes the game not very enjoyable- I queue up for normal and aram games to have a good time with 9 other people, but people like this just make the game less enjoyable.
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