why so hateful?

So I was just in a game playing top lane. I pulled up the score tab and noticed our adc had 9 kills live 5 min into the game. so I wrote in chat "man this cat already has 9 kills!" apparently calling someone cat (just the same as saying that guy or that dude). then for some reason the adc and his support decide to start calling me retarded for saying that.

I started giving it back to them (should have just muted right then) and they proceeded to say I was gay and that its a shame I wasn't in the Miami nightclub the night it got shot up. I made the mistake of using the work y'all in a sentence ( i'm from the southern USA) so they started saying that I had sex with my sister/uncle/various family members.

i'll admit that I didn't just ignore them like I should have but srsly what is wrong with people that you would talk to someone like that for no reason. I mean I was complementing the guy on his kill count.