Welcome to GTA Forums, sorry you've had to experience the nightmare of playing this game on PC in open public session.  There isn't much you can do against someone who wants to join you over and over and honestly my "solutions" aren't even ideal. You've got a few options:- 1) let him keep on doing that stuff and don't challenge it - don't rise to it or answer back, just let it happen. Eventually they will get bored and move on to someone else or give up entirely; 2) only play in invite