Being black myself PLove, I say don't worry about it. You aren't going to be able to talk someone who doesn't see black men into doing so. You don't want to schedule an appointment with someone who is apprehensive about seeing you in the first place. There are plenty of providers that will take your money. There are various reason why some providers don't see black men, even black providers.
You asked for reasons. Some reasons are legit, some are ignorant. The reasons are covered in-depth in the two links I have posted below. Read through them and you will be fully caught up:
http://www.eccie.net/showthread.php?...&highlight=nba
http://www.eccie.net/showthread.php?...&highlight=nba