Or the selection. "You'll just have to 'trust us.'"
Have the photographer show up dressed as Hitler. Full NAZI uniform, swastika, etc. Or maybe make sure the photographer is a a large dude dressed up as honey boo-boo except they have a strap on with a large phallic thingy hanging out. Put whatever is necessary in the contract to allow for this.
The bottom line is to not say no but put in to the agreement things that allows the photographer a lot of latitude. And, every so often dummy up a straight wedding where the exact same thing occurs.