All theory aside, its in poor taste and should not be supported. No good can come of this. In time, I'm sure you will agree.*dons flame suit*
Would I shoot it? Nope. Does it make gun owners look bad? Perhaps. Is it in bad taste? Perhaps. Should it be allowed? Absolutely. It's a piece of paper. I don't care if it's a picture of Osama Bin Laden, Sadam Hussen, Captain Crunch, The Virgin Mary, Travon Martin, etc.