Obviously, when this is applied to the common man in the modern world, it is false.
Especially when many of those men aren't even of good will, and who vote for the candidate that promises them more free benefits. Or they prefer something (like Abortion) that offers them convenience. Chalk this up to Original Sin.
Perhaps "the majority is always right" is a corruption of "The majority is OFTEN or USUALLY right, given a population of godly men"?
Because when this concept is applied to a limited group of more virtuous men (perhaps also with the limitation that you're not voting on something that can benefit you directly), it seems to be correct.
Examples: The Church trusts that the best Pope will be elected by the Cardinals during a conclave.
Religious orders think along the same lines. In the SSPX a Superior General is elected by the senior members of the Society. (Though in light of recent events, this seems to prove the contrary. Or perhaps it's just the exception that proves the rule!)
Also, the "people" of CathInfo seem to be virtually infallible in judging a post to be crap or awesome (Note: Any upvotes/downvotes totaling less than 5 are "noise level" and don't count)
There must be a way to define or distinguish this phenomenon.