There is some truth that actual hard-core racists love this, but I don't think you internalized Dr. Campt's message.

Once you do this, how have you not closed off any avenue to persuade the person to adjust their view?

Or, how do you know which are the racists who love this, and which are the people who just haven't thought about or adequately engaged their compassion enough?

If you take Dr. Campt's advice, the risk of rewarding any hard-core racists is minimal: if you let go of your anger, you're not actually upset. You just politely inform them that it is, in an abstract way, "upsetting". Almost everyone is after the emotional response, not a calmly applied label.

This prevents you from alienating someone before you've figured out whether they're reachable. Once you're positive they're not, then yes, I agree, admonishing them is a reasonable way to encourage them to at least shut up and not spread their nonsense any more.