I hear this a lot, and while there is certainly wisdom to be found in it, I wouldn't say 'always wrong'.
The majority of human beings breathe, doesn't make it wrong.
If you and I agree about something in a discussion, we are the majority in that discussion, doesn't make us wrong.
I think Mark Twain was a bit more accurate:
"Whenever you find yourself on the side of the majority, it is time to pause and reflect."
Printed copy · Anthology Volume 2, page 595Printed copy from The Tender For Law Anthology, Volume 2, page 595 (printed 14 June 2014). Added by this site; not part of the Facebook export.