Which brings up another interesting point. Are all the ycombinator staff comfortable with being accused of being racists? What would happen to any ycombinator staff who publicly objected to this accusation?
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.
The difference between this and "We are all sinners; all you can do is accept Jesus into your heart" seems to be merely a manner of terminology.
The only sort of racism that should even be considered these days would be genetic research of ethnic groups. That's not something evil BTW. Researching those prone to heart disease, cancer or have positive/useful genes that could be used to protect all of us in the future. Alas, we aren't living the movie Gattaca yet.