I’m not a lawyer, but I think there’s a legal defense under the DMCA, here’s the applicable part of the code:

(B) The prohibition contained in subparagraph (A) shall not apply to persons who are users of a copyrighted work which is in a particular class of works, if such persons are, or are likely to be in the succeeding 3-year period, adversely affected by virtue of such prohibition in their ability to make noninfringing uses of that particular class of works under this title, as determined under subparagraph ©.

Subparagraph C describes the process by which the Librarian of Congress reviews such exemptions, and specifically calls out non-profit and educational use.

AFAIK, this provision hasn’t been tested for a regular home user making digital backups of their copy-protected media for non-infringing use. There’s a plausible defense here: I can’t use a DVD player on my phone, so this law restricts my ability to make non-infringing use of the material I own when traveling without access to a DVD player (AFAIK, those don’t exist on planes or at campsites) or my physical DVD. So it’s reasonable to use a digital copy so that I can do non-profit research with the content on disks I own.

To me, that seems like a reasonable interpretation of the exception under this provision, and I think it has a reasonable chance of being upheld in a court of law. I don’t think it’s ever been tried, because copyright owners don’t care about people making backups, and they wouldn’t want to set legal precedent about this either. This argument hinges on whether ripping for home use can be considered “educational purposes.”

So yes, I’m okay with ripping DRM from a disk I own because I think there’s a legitimate legal defense. There isn’t a legitimate legal defense for piracy, at least not one I’m aware of.