Why are people so mean on the the internet?

[Mary]

Really?? With facebook, twitter, youtube and especially Instagram. I find it so strange that some people claim to hate drama, but use the internet as a means to embrace more drama??
Lots of people say its just ignorant pre teens fighting over the internet. But I've seen adults argue with each other on Facebook. I've seen adults argue with children too!
I know it's not easy to completely ignore trolls, but why do people feel the need to entertain the foolishness.
I've gotten more than my fair share of Facebook and Twitter attacks, but I usually read it and go on with my life. It really doesn't even faze me.
Why would I let a complete stranger or a person I barely know, upset me to the point that I make a fool of myself on the internet. Responding to the insults is never my first instinct. Most of the times though, the comment is removed in just a few hours.
Why do most people though participate in those ugly arguments. The simplest things can somehow make people say the awfullest things.
There was just an argument on my Instagram, about me having a nice butt or whatever. My friend took it as disrespectful, which was true, but it somehow turned into them wishing them to die, and kill themselves. I tried to calm them down, and the guy said he hopes I get raped!! What?? Why would he say something like that??
Usually I don't respond to insults, but my friend told him to kill himself, and that was after he told her she was so ugly she didn't deserve love. Why does this happen??