Give it a shot, get it on video
However the difference is a mosque is not a business (although I personally would argue that) it's a place of worship that operates on donations. Businesses must comply with federal, state, and local discrimination laws. Pretty sure a mosque, or church can get away with all kinds of discriminatory activity.
I guess if you're not into making gay cakes you could probably loop hole yourself into a non-profit religious bakery that makes cakes, and accepts only donations.