The "bubble" expression I've only ever encountered used by people from a rightish perspective to complain that other people aren't listening to them and that their perspective isn't the completely dominant one. Whereas people of the opposite view always know what the opposing view is - it gets shouted at them a lot - they just don't agree with it.
Anti-vaxers and flat-earthers might be called "bubbles", but then so is the pro-vax round-world view. After all, if you only ever read round-world media, aren't you closing your mind to alternative facts? /s
I've read enough flat Earth stuff to safely say I can reject it on its merits. Anti vax got started as a response to a series of industrial accidents that weren't handled right by the business side, but industrial accidents are rare so I think that's not sufficient reason to abandon vaccines entirely.
The only people you hear complain about bubbles are the people that are marginalized, if you agree with the bubble you will love every second of it and hate everyone outside. So, watch out before you speak in support of your bubble, that probably just means you are in the center.
Anti-vaxers and flat-earthers might be called "bubbles", but then so is the pro-vax round-world view. After all, if you only ever read round-world media, aren't you closing your mind to alternative facts? /s