Why not just let them leave and call the cops? That's what the cops are for. You fighting the guy is just unnecessary and pointless vigilantism. One of you will get hurt and you still may not get your DVD player.
I have rational discussions with criminals all the time. I work with a committee to disarm all prison guards and pass out pamphlets explaining to the inmates the importance of peace. I don't get why these violent Americans have to use guns to protect against criminals without first attempting rational persuasion.