What is with the URF community???

So I enjoy playing URF. It's a fun and interesting game mode that allows me to just let loose, and I don't even like playing the OPs everytime. I've played a lot of champs. From Draven to Thresh and Nidalee to Caitlyn. However, what I don't understand is how a mode that is supposed to be a fun and interesting experience, attracts some of the worst and most try-hard competitive people that I have ever seen since starting this game. Attracts the most vile and horrible people ever.

I've had to report someone the last 17 matches I've played in URF... I've been targeted with death threats, seen players claim "ez game" almost a dozen times while playing fizz, and watched as teammates and enemies alike drive down the morale and self-esteem of the players in the game. As far as I know, one of these players has been banned.

Why is this? Why does this non-competitive mode deliver the most hyper-competitive and vile people?

This could also potentially help Riot eliminate some of the horrendous people. Just send in some tribunal or player support members and have them scope it all out.