I've deleted the offending line. But I admit to being a little surprised that "ignorant fool" is considered a serious breach. That honestly seems fairly tame to me. I was looking for a phrase that meant that not only are they ignorant, but they're either unwilling or unable to recognize this. But I suppose I can believe that other people may read more into the phrase that I intended.
That is a serious breach of HN's civility rule and the sort of thing we ban people for. When someone is provocatively repeating wrong statements (or appears to be) and is getting increasingly rude, the way to deal with that is not to lose your own cool, it's to realize that there's no win in this and just leave it.
A.k.a. don't feed the trolls, it takes two to tango, two wrongs don't make a right, and sundry other things our mothers told us.