It’s a fine line. You don’t want to feed the troll and get yourself frustrated. It may be helpful to rebutt the poster but you should only do it if you can be perfectly infomative and concise. The more you argue with the poster the more onlookers might think both have valid arguments. Most people who are as divisive as seen in the OP have no problem arguing in bad faith. They will move goal post so frequently if you try to defend on all fronts you’ll look like you’re being tossed around.

Point being, general advise, ignore them. More specifically, it’s OK to rebutt them but don’t expect any reflection on their part.