Everyone is racist on some level, including those who would prefer not to be. It is deeply ingrained through constant cultural conditioning and has been shown to be true in many many studies.

It's much more worse to claim that you are in no way racist, since this just suppresses the problem. All you can do is accept that you have deep sub/unconscious biases and try to correct them in your conscious mind, though no one ever fully succeeds.

Eventually, hopefully, we'll all evolve in a better direction. In the meantime, this office hours is a good idea.