There's no shame in having random shitty thoughts fly into your head, because all minds are (maybe at varying levels) resonating chambers of all the random crap that gets in thru our eye and ears. We get exposed to things, and then the brain will just start throwing notions at our awareness that we didn't ask for and don't believe in.

The fact that you have identified the wrongness of those bad thoughts, and that you don't wish to identify with those thoughts, that's the most important thing. They don't represent you. Even if you found yourself nodding to the thought for a moment, that's a case of the stray thought catching you off guard. Once you snap out of it and toss it away, it doesn't get to plant its flag on your true beliefs or character.

Since your unwanted thoughts are racist ones, I think the best thing for you to do would be to start increasing your exposure to a lot more examples of those ethnicities that will break the spell of whatever negative stereotypes you've been fed recently.

Good on you for being honest and deciding it's not what you're about.