Shut Up and Say Thank You

Oh, I weighed 20 pounds less when that was taken.

It’s just the fancy outfit.

This? It must be years old.

Why do we do that? Someone compliments us and we have to immediately disagree. We have to set them straight, and show them that what they complimented is actually older, uglier, fatter, less pleasant, and just generally not as nice as they thought.

Seriously? Contradicting somebody and showing them how stupid they were to have thought that? How has this become polite?