People can force crash your game?

I tried buying a belt listed for best offer on the market and offered 1 less divine that was it was listed for as everyones currently up pricing i don't want to over pay for low rolls. The player then said if i dont pay the exact amount he would crash my game and before i could report him it crashed. Every time i logged back in they'd just crash my game over and over. Is there any way to stop these pathetic losers or what? I have his name and a video of him doing it if we can ban these players.

Thanks