You probably know more about DMCA than me, but I thought it was just about copyright infringement? The post claims the guy who complained in this case was complaining about "defamatory material".
It is just about copyright infringement (and some other types of IP). Hence the name: Digital Millennium Copyright Act
You never know with American laws. They seem to have a funny way of cramming in totally irrelevant nonsense into bills as a way of getting unpopular items into law.