Like I opened that post, they absolutely are within their rights to pursue this. I'm just saying the way it's handled is extremely poor, and only serves to get people upset about it.
UncleBob's right on this, the DMCA needs to be amended to have mechanics for people to fight back against false positives. Really, the burden of proof should be on the entity claiming infringement, but the way it is now allows big corporations to bully end users.