Something people seem to forget is circumvention isn't always illegal. You may circumvent copy protection for a work you own the rights to view, so the complaints about youtube-dl are poorly founded.
You didn't understand what I wrote. You can break copy protection if you own the rights to a work. This means you can e.g. circumvent Window's license checking if you own a copy of it already. The DMCA does not criminalize that, nor could it, and this is probably why py-kms is still up on github after a copyright challenge.
This was a change that I am assuming was added before any complaint could be mounted about this use case for fear of striking more of the DMCA down than just that provision that was modified.
The supposed excuse of that overreach in giving the Librarian of Congress the ability to define exceptions is totally lame and unacceptable.