I've knocked them out with a punch and never had a problem. Ever seat a primer in sideways?
But yah! make sure you have eye protection if you use a punch. have fun and be safe
Let me add to what I said. The anvel needs to be firm against something in order for the primer to work with a blow or impact. Chances are that you could hit the primer hard and nothing will happen being the anvil in out in the open. But always make sure your eyes are protected before you hit a primer just to be on the safe side.
That being said I know a guy that lost his right hand storing primers in a baby food jar. A few hundred primers going off at one time is nasty. I was not suppose to happen but it did.