I think the guy was testing how good you are. The problem with most magicians (no offense) is that we have to be in control over everything to get the trick to work, and so very often do we give the spectator any kind of part in whats really going on. For those of you who read "Card Ideas" you know that about half of those effects Simon's back was turned while the spectator cut to a card and shuffled the deck. For those of you who havent been studing your magic history (shame on you), in the vaudville days of card magic, the spectator would return the card to the deck, and the spectator would shuffle, then the magician would find it. It's almost silly to suggest that if you put the card back into the deck, and if you shuffle it, that its magic when you find it. I dont think this guy was being a jerk, I think we wanted to be completly fooled. I try to be as fair as possible when I perform as well, most of the time cards are not selected they are either named, or I riffle very slowly with my head turned away while they call "stop", its very fair and with the right effects, no one grabs the deck. Or maybe the guy just picked up on the fact that you where nervous and decided to give you a hard time. In which case, try not to be nervous or it'll keep happening.
You don't think that he was being a jerk but he think that he was giving him a hard time? Your contradicting yourself a little there.
If the guy forcefully pulled the deck out of his hands and told him that he "blew it", becasue he wasn't getting "completely fooled" then he was
being a bit of an childish a**.