Why would wide applicability be a mark against an idea? Do you feel the same way about gravity and normal distributions?

Your example is an excellent one though because it shows a corollary to the way that quote was intended in this conversation.

How it was meant: "It's OK to not remember everything you've read verbatim, because the important parts mixed into who you are/were."

Your corollary: "We must be careful about what we consume because it will be mixed into who you are."

That last sounds a little bit Vonnegut: We are what we pretend to be, so we must be careful about what we pretend to be.