But yes it does sound like bullying to me. Your decision is whether you'll call or fold, based on the cards in your hand. And don't think of it as winning or losing - you have nothing to prove and the web owes you nothing - make the decision based on whether it's in your best interest to keep the content or chuck it.
BTW, you are allowed to take that C&D letter and post that on your site, to show the public how BRANDNAME is throwing lawyers around to manipulate public opinion.
If you're feeling cheeky, you can present it like this:
<li> blah blah blah
<a href='letter_from_brandname.html'>THIS CONTENT HAS BEEN REMOVED BY COMMAND OF A CEASE AND DESIST LETTER FROM BRANDNAME. THEY DO NOT WANT YOU TO READ ANYTHING BAD ABOUT THEIR PRODUCT. CLICK HERE TO READ THE LETTER, THEN FORM YOUR OWN OPINION.</a>