He didn't say a grab, he said a strike.
Its about the worst thing you could do for several reasons. The main one being that the person you're striking in side control has a much more dominant position than you have, so if you start trying to punch him, he'll start punching you back, or he'll begin to apply nasty pressure tactics like jamming the blade of his forearm across your neck, adjusting his weight so he is compressing your chest, or smashing your head into the ground with his elbow.
If he is a submission grappler, he can easily apply arm locks or chokes once you start trying to punch. Your punch has next to no power backing it, so even if you hit his temple (which in of itself is a longshot), you have an incredibly low chance of knocking him out. And that's assuming that he hasn't trapped your arm at this point. Worse, if you're against a skilled grappler, he'll let you start punching, to make the trapping easier. Some of the nastiest chokes in side control comes from trapping the arm against your opponent's neck, and you trying to punch his temple makes that trap a lot easier.
This is why its curious that there are no anti-grappling vids for side control. Side control is a far more dominant position than the guard, and a lot more grapplers use it than just Bjj. Of course, given the laughable guard passing stuff, the absence of side control escapes doesn't surprise me. And if you think I'm giving grapplers too much credit, ask Steve, Tony, Drop, or Brian what its like to grapple against someone who has never grappled before. It's like they've fallen into an ocean and you're a shark.
The ironic thing about all of this is that there are comparatively
simple ways to get out of side control using grappling. I don't know why you guys insist on making things hard for yourselves.