He threw open-source developers under the bus in the process. As a result approximately nobody writes GCC plugins, open source or otherwise.
> It is not our goal to “help Windows users” by making text editing on Windows more convenient. We aim to replace proprietary software, not to enhance it. So why support GNU Emacs on Windows?
> We hope that the experience of using GNU Emacs on Windows will give programmers a taste of freedom, and that this will later inspire them to move to a free operating system such as GNU/Linux. That is the main valid reason to support free applications on nonfree operating systems.
RMS has been exceedingly clear about his views for decades. At this point it's hard to be surprised that he’ll make a pro-Free Software decision every time, without fail. That doesn't mean you have to agree with his decisions, of course! But to be shocked or disappointed by them is a sign of not understanding his platform.
RMS: Here’s how they'll get ya!
Me: Nice, but that'd never happen.
Vendor: Here’s how we got ya!
Me: Dammit.
Seriously, he must have a working crystal ball.
Now, my agreement with him starts and ends on that subject. He says plenty of other things I wholly disagree with. But his warnings about proprietary software lock-in? Every. Single. Time.
Also, if you want Windows to die you need to work with OEMs: I assume that most users simply use whatever OS is pre-installed.
With OS X on one side, and POSIX subsystem on Windows NT/2000 side, everyone would be doing their UNIX like workflows without thinking once to try out GNU/Linux.
At my university we only cared about Linux on its early days, Slackware 2.0 days, because naturally we couldn't have DG/UX at home, and that POSIX support was really unusable beyond toy examples.
No, this is giving him too much credit. His stance on gcc wasn't just purity over pragmatism, it was antithetical to Free Software. The entire point of Free Software is to let users modify the software to make it more useful to them, there is no point to Free Software if that freedom doesn't exist - I might as well use proprietary software then, it makes no difference.
Stallman fought tooth and nail to make gcc harder for the end user to modify, he directly opposed letting users make their tools better for them. He claims it was for the greater good, but in practice he was undermining the whole reason for free software to exit. And for what? It was all for nothing anyway, proprietary software hasn't relied on the compiler as the lynchpin of its strategy for decades.
Expecting Stallman to make life easier for commercial vendors is like expecting PETA to recommend a good foie gras farm. That's not what they do.