I'm sure that Tomlin could "ham it up" on the sideline so he gets the cameras on him at least a dozen time a game.
I never had a problem with the "unleash hell" comment. Tomlin was trying to set a tone. It was the players on the field that failed. What did you want Tomlin to say "we'll try harder?"
You are criticizing Cowher for "hamming it up" to gain attention, but don't find "unleash hell" to be equally attention whoring, to use your interpretation (personally, I think that was just Cowher's personality).
In any event, I'm not a big fan of comments that are full of bravado, and like them less when they are not backed up.