This does not mean ignoring it in all cases. It simply means to remember you are dealing with an obnoxious precocious 9 year old. Explain once, pat them on the head, smile indulgently when they repeat it themselves, tell them someday when they grow up they will understand, and move on. When pressed by others, sigh and provide them with your pre-canned answer. If you've written it down, you can usually get this down to a "No" with a link.
As with all things, balancing between ignoring the comment, responding as I have described, or genuinely engaging depends on circumstances. You don't want to exhaust yourself, but you don't want to let things spread until it becomes a "Thing." A categorical decision never to lower yourself with a response leaves you vulnerable to manipulation. Engaging in a tit-for-tat runs the risk of creating a false equivalence. Find the sweet spot in between.
As with all things advocacy, remember your true audience is not the annoying troll. Your true audience in this case, are those new to the debate who have no idea of the history. They are easily confused by such arguments and are not going to research it themselves. You want to be condescendingly indulgent to your trolls, but genuine and patient with everyone else. Remember, people who don't follow this closely can be easily confused by surface similarities. That's why
