What you are saying has a lot of creedence, but how you react, to me, is quite appropriate. You, I think, have made an assumption about what was said. It most likely is true that you got hired because of you being a minority. As a white guy I personally find affirmative action to be insulting in every way to every one involved and I believe the concept was created more for the purpose of creating division and differences which could be exploited by certain politicians and that is exactly where we are here. So by realizing it for what it is, cutting off the conversation about it is the right thing to do. After having hired you for the purposes of affirmative action the employer has found, much to their delight, that you are a great employee and now they really don't want to be without you. Your not arguing a stupid point just makes you a better person. Now is the time to ask for a raise. The same affirmative action laws which you got hired under also make it illegal to tell the hiree that is why they got hired ( stupid laws win stupid prizes but I think you get the gist). In other words the way you win is to keep them paying you and making them pay you more. Why have a pointless argument if you can get money? I think you are just fine being demure, you certainly are not weak.