I didn't realise how important free software was until I started using an ARM laptop for day-to-day work. Absolutely tiny userbase, barely any binary packages, but I could clone and make my way to everything I needed. Without RMS and GNU, free software would be nowhere near where it is now.
It's obviously impossible to know that, so instead of nitpicking, let's graciously interpret it as acknowledging that he (et al) did contribute a great deal to the foundations of free software we have today.
I'm not claiming this to be a priori knowledge; that's how causality works, I don't know that Barack Obama was elected because I chose not to eat a cheeseburger in 1999. RMS laid the foundations for the free software movement, growing the open culture and creating a good licence. I think it's hard to debate that what RMS has done hasn't improved the free software landscape today.
How does GNU and free software justifies his claim that we can be in control of our software? I think RMS doesn't like Linux but being an open source software it still can be injected with potential backdoors. What makes him think his software won't? We still review code but your average Joe cannot code and he won't code. So he's going to use a software someone packaged. How can you tell if no one will ever inject a backdoor?
edit
This is a major point he always makes about security. I am not buying his total obsession with GNU because that can't be prevented.
Obviously open source is not a guaranteed defence against backdoors, but it gives us the opportunity to look for them. Closed source software does not even allow us that, so it is inherently untrustworthy.
This is sarcasm, I'm guessing. The suggestion being RMS wasn't a crackpot at all. We were (well, most of us were) just naïve and didn't think much of his advice back then.