Why Sasuke fans use this logic.

[Sennin of Logic]

This right here is very true. I hate it when people say that he tanked/stopped a "moon busting" attack. That's just all kinds of wrong because the attack only needed so much power to penetrate the moon. It only had a huge range.

You're ignoring thickness. A phone book can be tough not because the individual papers are strong (they're weak), but because so many of them are stacked on one another. Toneri's attack had to have the power to pierce through countless amounts of rock in an instant to cut through the moon like that.