I would definitely give concrete examples to your therapist. A longtime friend of mine is a black guy and I witnessed what he goes through first hand. (We recently attended a friend's wedding and stayed at the same hotel, he approached the concierge counter and a white guy practically jumped out of the way. My friend is one of the kindest people I know and witnessing this made an impression on me)

I think people want to believe it doesn't happen anymore but it does. Subtle racism is particularly cruel because you feel it, but others may not see it.

If your therapist continues to be dismissive, it may be time to find a new T.