I'm all for it. As a woman I have had very bad experiences with Muslim cab drivers. They are frightening and rude. They can't seem to get the idea that women are allowed to travel alone without a veil.
Once in Minnesota I had a cab driver that --- no kidding --- looked very much like Mohammed Atta, who glared at me, tore around the icy streets at high speed, almost snarled at me when I asked a question, seemed very agitated and angry to the point where I simply asked him to pull over and I got out and walked.
I would love to be able to avoid Muslim cab drivers carrying a big bag that says LIQUOR STORE or something. Hell I would wave a bottle of Johnny Walker at them to avoid getting into a cab with a Muslim driver.
Get a dog! I have the opposite problem. My complexion makes it hard to determine my nationality and for some reason, I keep getting marriage proposals! As for the cabbies talking on the cell phone, yes it's not safe but at least it keeps their attention off of me. Ever since this became common practice, I haven't been bothered with unwanted questions about my family, my marital status, etc.