This is a simple matter to resolve.When a pervert couple demands a cake from them they should make it but leave out one or more essential ingredients (sugar and vanilla extract,for example),thus making it inedible.When the perverts come back demanding a refund you apologize profusely for the error and give them their money back.Word will quickly get around the pervert community to avoid that bakery.
"Here's the wedding cake that you forced me to bake. While you enjoy it, think about the fact that, thanks to you, I've incurred substantial legal bills and had my business and very livelihood put in jeopardy. Both myself, and my family have been subjected to numerous verbal and physical threats from you, and people just like you, for no other reason than you felt the need to score a few political points at our expense.
So.........Bon Appetit!!"
Man, I'd not want to get within 1000 yards of a cake like that.