"How does it make sense to claim software is free-as-in-freedom if it's designed with DRM or other anti-piracy measures? "
I think the pro "Tivoization" argument was that just because I'm obligated to share what I have done for free or nominal cost - possibly for educational value, I don't have to make "easy" for you to simply copy and use my work, and not put in your own blood sweat and tears. GPL 3 was intended to clear this up - I do have to make it easy and cheap for you to use my derivative - and legal - if I distribute my work. BTW Linus T. didn't agree with this change according to some articles I read. He was OK with Tivoization so long as he got to see the source code of the derivative.
"Can you even technically pirate GPLed software to begin with?"
Maybe. You aren't required by the GPL (either version) to distribute your derivative work. Only that you don't limit the rights of those you do distribute it to, - if they are outside your organization. Within your organization, for instance, Google or Amazon, you can have custom versions of GPL'd software that are trade secrets and could presumably use DRM to stop the distribution outside of your intended internal use, or to track who let it loose.
So getting a copy of a private version of a GPL'd derivative, intended for private use - could be considered piracy.
Just a thought - not dogmatic about the thought at all.