My experience has taught me that what he should have done in response to the initial information, ie “your hashtag doesn’t mean what you think it means,” was to respond, “Oops, sorry. Didn’t know,” and move on. After that, when the trolling started, a better technique instead of responding would have been to block those people. That’s what I do. I no longer worry whether I have “good reason” or not. I don’t like it, I don’t waste time on it. I just block.