No matter how it turns out it there will still be a double standard for firearms and those who sell them.
It's a Civil Rights violation to refuse to sell a house or Rent one to someone because of (Race, Color, Creed, etc.) same standard could be applied to the refusal to sell a gun to someone simply because of their (race, color, creed, etc.)
What makes you think for a second that there aren't any Islamic FFL's (roll in Muslim, Arabic, Middle Eastern, etc.) I clearly remember seeing and even dealing with them as far back as the 80's
Mexicans smuggle shit-tons of illegal Drugs into the Country; I find it hard to believe there aren't other things brought in by the same.
History even recent is full of examples of young, radical, Islamic terrorists committing heinous crimes
supposedly in the name of Allah....I'm betting they didn't buy any of the weapons they used legally or on the open market.
People in Business really cannot be honest about their dealings either with customers and for damn sure with the government, so I suppose if you don't want to sell to someone whose not of a religion you approve of, you'd better have you story straight and not deviate from it; in fact the less said the better.