He didn't label you a racist, but I can understand why you would feel uncomfortable if you felt he did. Rather than lashing out and holding a grudge, maybe you could have responded along these lines:
'i don't believe I am a racist, and I'm mortified that anyone else would think i am one. Can you let me know why you thought that?'
You might have learned something. You have said elsewhere that you like to analyse and understand things.
He did! Read the words! He kept at it, then others supported him, including you! If you're able to comprehend simple sentences and you actually care what I think, why haven't you corrected him and withdrawn what you posted and apologised? What's wrong with you?
He didn't label you a racist, but I can understand why you would feel uncomfortable if you felt he did. Rather than lashing out and holding a grudge, maybe you could have responded along these lines:
You might have learned something. You have said elsewhere that you like to analyse and understand things.