Although this user acknowledges the logical fallacy ad populum, they do not think that it applies to human language, and recognise that the majority determines grammatical "right" and "wrong".
Majority Usage = Correct Grammar
This user recognizes that if most people make the same grammatical "mistake", it ceases to be a mistake and becomes proper grammar, for grammar has no immutable or moral "right" or "wrong" and "correct grammar" is determined by majority usage.