As the article points out, the TPM is not in a good place, architecturally, to use for DRM: there's no path from the TPM to the screen that's not under OS (and thereby user) control.
If you modify it thanks to remote attestation you can no longer prove that it is unmodified using the TPM.
In Android phones for example you cannot screenshot banking apps. And if you root (modify the OS of) your phone, banking apps refuse to work.
I'm not saying that the TPM is incapable of being abused by manufacturers and OS authors, but the FSF really weakens their argument when they predicate it on something that's not actually true. Ex falso quodlibet (you may prove anything if you rely on a falsehood).