Why are League players so mad?

Soloing dragon with Vi got me wondering how early Warwick could solo. There's a video of a guy doing it level 1, so I thought I'd load up a co-op and try it out just for fun, not really expecting it to work. Another guy locked in jungle, though, and when I told him my plan to just try for level 1 solo dragon then lane for the rest of the match, he said I was muted and reported. (He also joined me and wouldn't leave, refusing to let me even attempt to solo it)

And in URF one time I had a guy who spent literally the entire match nitpicking everything I did, telling me I was stupid and doing this wrong and that wrong, and he acted surprised when I lost my cool.

It's like this every match in every match type, more or less. There's usually at least one person who gets salty and/or toxic for silly reasons. Most of them have an undeserved god complex as well. For a game so focused on teamwork, I don't get why so many get this me-against-the-world mindset and act like everyone else is doing everything in their power to hold them down.

You see it in all the threads about how this and that is why someone's stuck in bronze, not their own play. No, you're never at fault, not even when you spend the entire match being overly critical of everything your teammates do, and have to pile on even when they admit their own shortcomings. "Sorry, I sucked that match." "No, you didn't just suck, you swallowed that ****."

Even the more mild mannered of us can't seem to restrain ourselves from giving in to the trolls. If you don't mute the idiots, and you waste time and energy arguing with them, it's just going to dig you deeper and deeper. You can still win with your garden variety toxic/trollish player if you just focus on the task at hand rather than telling them what's what.

Maybe it's just easier to be mad at the world than at yourself. It's how teenagers approach things, so perhaps League's comprised largely of teenagers or people who never grew past that stage. If I lose, I feel sick to my stomach and start analyzing my performance for things I can try to avoid and improve upon next time. In rare instances I'll find plenty of other culprits in the loss, but in those sorts of matches it either was never going to be a win or I didn't carry hard enough, so what's the point in getting mad?

Just... why? Why must every player be one mistake by a teammate away from evolving into a troll? Why must people treat even co-op and URF matches as if they're ranked? Why must everything be so damned high stakes? I'm really starting to tire of it.