TRHit - I guess I am willing to consider that there is more to this story and to give you some credit on this, instead of judging by all that we know so far. It doesn't sound like something I would do, but I am curious about a couple of things:
1) You stated that we don't know the relationship that you had with the family and the player. I agree with that. Are you asserting that your relationship with them allowed you in good conscience to bring up his ethnicity with the coach?
2) If the coach, instead of silence and then shutting down the conversation, had asserted that the player's ethnicity would be no problem for the school, would you have then discussed it with the family/player? If this is the case, I could see that you may have rooted out bigotry on the other end rather than displayed your own.
Just curious and trying to think outside the box of the other replies.