If you're still having trouble convincing them it's in the Player's Guide under Mind Control clarifications:
A character that is successfully hit by Mind Control cannot use any game elements assigned to it during force construction until the Mind Control action resolves.

Right. Earth Man is looking for a specific kind of action: he doesn't care if it's as a free action or non-free, he just wants to see "power action" and he says "nope, don't think so".