Depending what exactly you mean by "ideological purity," I might somewhat disagree with you.

I definitely want there to (continue to) exist an organization pushing for all software to be FOSS. If the Free Software movement didn't exist but the OSS movement did, I expect there'd be much less FOSS out there. There are a lot of projects out there that don't have a good OSS movement reason for existing. Coreboot, for instance. Arguably to a large extent Wine as well. And LineageOS and GrapheneOS. And OpenWRT. Not to mention ~(GNU/)~Linux itself. I don't imagine most OSS folks to be quite so motivated to want fully-FOSS-from-soup-to-nuts kind of options as Free Software folks are.

There are plenty of software companies publishing more proprietary software for Linux and plenty of OSS folks heralding that as a huge win. For the most part, I see that as unfortunate. And I have reasons why that I can point to that wouldn't be seen (well... quite as much, at least) as tinfoil-hat levels of paranoia.

And then there's copyleft. I think that's a fuckin' great thing that's needed more now than ever, but (and I don't know for sure... correct me if you think I'm wrong, but) I think that's more of a thing among Free Software folks than among Open Source folks.

And I don't think any of the above could have come about or at least been quite as prominent today as they are without such an ideologically-motivated movement. The FSF put a very aggressive line in the sand saying "proprietary software shouldn't exist." Basically the main thing that distinguishes the OSS movement from the Free Software movement is tolerance of proprietary software.

Also, I don't really know for sure the extent to which this is actually the case for OSS folks as a whole, but ESR's "the solution to everything is more capitalism" is pretty fucked up.

That said, I 110% agree the Free Software movement needs to be doing mostly everything it can to distance itself from RMS.