The thing is using piracy as the justification for DRM is always going to be the greatest excuse, because it's one of those technicalities you can never truly argue against.
No one is ever going to tell you that piracy isn't bad. Piracy as a concept will always be seen as wrong (and rightfully so).
But without any hard statistics on piracy, AND the methodology behind those numbers, piracy gets to be this wonderful boogyman where you can't deny it exists, and can be used to justify whatever DRM solution, but without ever needing to prove how much of an effect, if any, DRM actually has on the overall return.
I would be more sympathetic to the DRM/anti-piracy crowd if GOG didn't both exist, and seemingly thrive. They literally hand out .exes that people can just re-upload on torrents sites or UseNET or whatever, and yet games still release on there, and they still (seemingly) sell well enough to justify continuing to do so.