No way.
Would you cater a KKK rally? Would you cater to a child nudist park? A NAMBLA convention?
I think the whole point is that the potential customer would run screaming away from your business, not that you would end up serving them chi-rho wedding cake
whats a child nudist park?
I see your point, but more than likely, the trouble seekers will move on.
Letting them know that you will openly pray for them and ask grace over the food might be enough to chase them away.
Meanwhile fight this in court and with laws to protect a business’ right to refuse business to anyone for any reason.
Hoisting 'em on their own petard may be the way to go. Find a Muslim-owned bakery and request that they decorate a cake with the words "Allah is Satan, and Muhammad is his pedophile". Then sue if they refuse. But be sure to bring backup!
Think about it though. Chances are, if there is full disclosure, they’ll take their business elsewhere.