Bake the damn cakes...but....put a little extra ingredient or two in to insure that the alimentary canal is not blocked in any way. IOW Montezuma’s revenge to the max!
Easy to identify and trace, he’d end up in jail on assault charges.
There’s a better idea: simply say that for every gay wedding cake he’s compelled to bake he’ll donate the profits to one of the number of Christian organizations that provide services to flip gays straight.
Problem will quickly solve itself.