I'm not VLM, but yes, peer-pressure in another guise. Just think about your attitudes and beliefs on (a) handgun ownership, (b) creationism and (c) Israel. It's very likely that if you're in a social group with strong homogeneous view on one of these items, that there will be a matching "party line" on the others - even though they're completely unrelated. Chances are low that you'll argue the point, you'll probably just stay quiet - but many people will enthusiastically take that party line as their own.
I think that's just groupthink. People tend to act on their beliefs about things like vaccines, Israel, and handgun ownership.
Of course, it's one of the earliest results in psychology that social conformity has an influence on people's beliefs, even on readily accessible questions like whether line A is longer or shorter than line B. To me, if somebody professes a belief, acts on that belief, and works to convince others of that belief, then they effectively hold that belief.
