If it was their own cabs, they should have the right to deny such ads on the top of their cars (much like I thought it was acceptable for having the baker deny making a wedding cake designed for a gay marriage, since it's their business, even though realistically it hurts a potential revenue source)...but they work for a larger cab company, so, they have less control over the cars they drive in.
Basically, form your own cab company, and choose the areas you operate and the advertising you want to use.
N_Fiddledog N_Fiddledog:
I say it's because in politically correct poker Muslim trumps any other minority.
There was that one case in Canada involving a Muslim barber refusing to give a gay woman a man's haircut, but that one was settled out of court.
See, I agreed with the position of the Muslim barbers in that case. Neither article I read had anything to do with her sexual orientation (oh I can make assumptions, and so could they, but there's no proof that played a part) and the reason why they weren't willing was because as Muslims, they can't touch a non-relative female's hair. The woman in question was all pissy even after the barbers found somebody willing to cut her hair in the shop, as she wanted to make some point against these guys who just want to run their business.