That’s extremely weird, I’ve never heard of Firefox not letting you browse until you update. When snap auto-updates Firefox there’s usually a notification bubble asking to close your browser to update but you can dismiss it and keep browsing in my experience.
This will be unpopular but I wouldn’t defederate it just for having shitty politics just like I don’t believe in defederating the “Tankie” Lemmy instances for their politics. As long as they’re not shitting up the rest of the lemmyverse like the way r/The_Donald used Reddit like a fleshlight from 2016-2019 they can have their little corner, who gives a fuck.