if someone did that to me i would want to kick them in the face, that doesnt mean i would i might just kick them in their stomach. no one has tried to whack my cards out my hands, i just seem to know how to control hecklers.
really, use ur mind against them, i use my words to shut them up and go away. thats the best thing to do
Depends. I've never had to resort to physical violence. Partly because I'm a professional.
I'm not saying you should outright assault the guy. I'm saying, knocking something out of your hand goes beyond heckling, and borders on starting a fight. I truly do encourage clever use of audience control in order to retaliate against the responsible party, but also realize this isn't, "Well I'll just pick up the cards and wow him with a strong self-worker!" I've never run into such an instance, but I can imagine if someone got physical (snatching something from me, knocking things from my hand), then that would at the very least pause the performance to ask what the hell their problem is.
This is, of course, implying a casual venue, where you're on your own, like busking or at school or something. I'm aware there's better ways to deal with it if you've actually been hired for your performance, but I'm not talking about that.