The main thing I want to convince you of is to flag this type of comment - a thing everyone should do! The engaging (or not) is more practical thing - avoiding the risk of a giant thread of meta sitting at the top of a submission to the detriment of actually interesting discussion. Since everyone loves meta and bickering, this happens quite a bit. If the comment is safely at the bottom of the thread, engage away. I sure can't seem to help it. It just does a lot less good than flagging (which is not just for trolls and flamewarriors).
