DD first off let me say I am sorry you had to put up with the attitude from this player. This is a tactic I have seen tried by a few folks over the last couple of years. They do it to get players off their game, or they think it is fun to be an inet tough guy. My advice is go to your account (radio button above the play now) and go to the block players tab. key in the players name and forget em.
As for turning the chat off, I am unsure about off but you can close the chat tab, it will still show orange if someone types something but you can ignore it. I often play with it closed and will put a small windows calculator over it so i don't see it blink and I can use the calculator for quick dist calcs.