I often get preached at about how bad social media is. The irony is that I don't have any, and the people preaching at me do.
My best theory: I suspect both online and offline, people "parrot" ideas 90% of the time. They hear an idea, repeat it without much thought, if it resonates well they repeat it more.
I think the reason people do this in-person is the same as they do it online. They say things not because they have deeply reflected on all the ramifications and sincerely believe and live by those ideas. They say things "to get likes."