I think this sentiment, if taken literally is a tiny bit oversimplified, but it's probably the correct approach most of the time! I find it a great starting point at least to guiding my behavior.

Maybe Mark Twain's adage is more subtle, that if you find yourself in the side of the majority it's best to "stop and reflect."

I wonder what the hell is going on that makes this so true? Are humans just hardwired to do the dumbest shit possible as a group? I've heard people say that individuals are usually smart but collectively we're dumb.