How can I convince my mother to accept my boyfriend ?

So, why haven't they met? Tell her that if she had objections to him as an individual as opposed to his entire race in the abstract, then you'd be more inclined to take her seriously. But until she meets him and still thinks there are concrete reasons he specifically is wrong for you, then you don't want to hear it any more...and that means that until she's at least willing to try and overcome her prejudices, she's going to be missing out on a big part of your life. She doesn't want that, does she?