Comparing the SSPX saying its not inherently sinful to take the vaccine to a Jonestown cult that actively encouraged people to commit ѕυιcιdє is a massive stretch.
I don't think I believe the vaccine is OK to take, even if I was convinced it was theoretically acceptable I would still have enough good sense to not take it. Is the SSPX really "encouraging" taking this vaccine?
You have to distinguish, at the least, between that, and just an allowance that reception would be theoretically not sinful.
And again, I'm not condoning their position. I'm just saying be fair