I'd not even go that far.
I'd bake the cake. And deliver it. With a big smile on my face, and a note....
"Here's the wedding cake that you forced me to bake. While there were plenty of other bakers who would have appreciated the business, you chose to force me to perform this service for you, for no other reason than, "You Could".
"While you enjoy it, think about the fact that, thanks to you, I've incurred substantial legal bills and had both my business and very livelihood put in jeopardy. Both myself, and my family have been subjected to numerous verbal and physical threats from people just like you, for no reason other than you felt the need to score a few political points at my personal expense.
"So.........Bon Appetit!!"
Man, I'd not go within 100 feet of a cake like that.
I hear ya...but you've gotta remember that they're wired very differently,morally and ethically speaking.They would derive almost orgasmic delight (pun *absolutely* intended) in reading your note and passing it among their many pervert friends.
Just sayin....
Anything that is not an outright refusal will be regarded as a win by "Big Anus".
You can couch your defeat in any rationalization verbiage you want, but the only way to win is to say "No. I will not do it."
They don't care how bad the cake is. What they care about is the fact they forced you to normalize their behavior.