You reacted as you saw fit, to what was presented to you. For that I applaud you, you did nothing wrong.
At times I'm a bull in a China shop, engaging mouth before putting mind in gear. I have many first hand experiences of racism, most of them do not come from the likes of the subject of this thread, they come from what you and me would describe as "normal" people.
As much as I'd like to just switch off the people I don't agree with, life doesn't work like that. To listen is to learn, from that we may be able to educate.
To ignore someone just because you don't agree with them is a big mistake.
Like you say though, onwards and upwards. X
P.s. doc, I've enjoyed engaging with you, you speak very well.