boyfriend and another girl?

So the other day my boyfriend was out riding and some girl that likes the same things he does and kinda seemed like she was flirting with him recently hit him up on Facebook. He was telling me about it and was telling me that she asked to hang out with him and that he kinda wanted to because she's black and likes all the same stuff he does. I got mad and told him no. He got kinda mad that I said it. Was that a bad thing to do?