Sure, just put him on your block list.
unsportsmanlike behaviour

If a player refuses a draw with a king and rook each and insists on playing on to 100 moves can I avoid playing him again
Not sure why it is unsportsman-like to play on.
Sure it is a draw at serious player level, but for most folk on here making a mistake is quite likely. The best way to ensure that you will never in your life lose in a position like that is to actually play it multiple times.
If a player refuses a draw with a king and rook each and insists on playing on to 100 moves can I avoid playing him again