Does that make me a porn racist?
Well if you want a real answer, we would need to know more. It's about WHY it bothers you.
Note, porn with black men having big black dicks is pretty racist. It often portrays black men as dehuman, who can't control their lust to white women. VERY common on games on this site when you deal with NTR especially. The concept of all black men having a big dick is also obviously racist. Note, this also goes both ways, being racist to white women as well. The point of most of these videos is to create a feeling of taboo, and the taboo is there because of racism.
So if that behavior turns you off, then it's not really about the skin color.
There is the argument of preference, if something doesn't turn you on then it doesn't turn you on. There is nothing wrong with not being attracted to big boobs, and it's also nothing wrong with disliking small boobs. You like what you like.
Saying that, everyone is racist to a degree. I try to be egalitarian and treat everyone equally but I (like EVRYONE) was taught racist things growing up and that shaped our tastes. While I try to not act on these things, they are there and I don't always realize they are there.
My point is don't stress over the little things, even if it is because of the skin color. As long as you are not telling other people it's wrong then no one should care what you like.
TLDR: Don't stress over it.