The real question here is not one of information freedom, but one of trust.
If I were to send you a GPG-encrypted email, it's a relationship of mutual trust: I know that you have full access to the information, and can do with it what you want. However, the ISP/NSA/GCHQ/KGB do not have access, because they are naturally not trusted.
DRM is different: if I distribute content to you using DRM, I am saying that I do not trust you to have the unencrypted content. Furthermore, DRM implies control over the hardware and software used to play content.
If I were to send you a GPG-encrypted email, it's a relationship of mutual trust: I know that you have full access to the information, and can do with it what you want. However, the ISP/NSA/GCHQ/KGB do not have access, because they are naturally not trusted.
DRM is different: if I distribute content to you using DRM, I am saying that I do not trust you to have the unencrypted content. Furthermore, DRM implies control over the hardware and software used to play content.