IAAL (but not a practicing one, so I don't have skin in this game, and this is not legal advice). I also once lost $25k+ in a copyright litigation relating to music piracy before I became a lawyer. It was decidedly not fun.

You ignore a C&D at your peril. The rules are complicated and the fines and penalties for not following the rules are expensive. U.S. IP law is fiercely protective of patent rights, trademark rights, and copyright. It's not something you mess around with, and anyone who tries to defend himself without a lawyer is a god damned fool. The author of the blog post did the right thing by engaging and trying to work something out without coming across like "go pound sand, I do what I want."

Please don't walk around giving bad advice like this. I pray for the poor sap who listens to it.