Comment by KyleJune
One way people keep themselves in bubbles is by dismissing counter opinions as being tribal or trendy. Some opinions may appear that way because the people that have them seem similar. But it could also be due to them having similar backgrounds that led them to those opinions. For example, most doctors believe in vaccines, but that's not group think, it's based in evidence that they have studied. From the outside, it might seem like group think.
My method to discern between beliefs with intellectual backing and those from the community is by presenting them with some bizarro counterargument. If they copy/paste specific phrases and keywords, it's from the community. If they engage with the argument and refute it, then they have given them proper thought.