I make a parallel with politics and transparency, a software lead once told me that a completely transparent government was tried in the french revolution and it kind of didn't work. For example, we all would agree that there's some functions of government related to war and security that should not be transparent. I feel that free software would obsess over that private fraction because for all you know it might hold all of the secrets and evil that you imagine.
That said, it is possible that under the guise of reasonable need for private blobs/three-letter-agencies, a lot of other 'evil' things may be hidden. Maybe they say it's due to security or IP concerns, to provide protection against device tampering, to avoid pollution of radiofrequency spectrums, but it's possible that in reality they are hiding spying software in the wifi firmware and hardware keystores?
I feel that if the FSF recognizes that there's some areas that are ok to have closed source, then they could be taken seriously, otherwise they will just be ignored and leave room for precisely the kind of misuse of closed source that they fear. This is especially noticeable when they fight against projects that precisely do a lot for open source, like github (See GitLab/Savannah), or Android, they are 99% of the way there, give them a break.
Extremism begets extremism, if the jails are too full (or too empty), advocating for the other extreme will get you nowhere, the Overton Window doesn't quite apply, in fact it can be harmful as you are providing a real threat to the other extreme.