The actual quote reads: "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil."

O(n) vs O(n^2) is not a small efficiency for non-trivial data sets. This is the point that was being made. Many people forget that the quote hinges on the word "small" and then use that as an excuse to disengage their brain when it comes to basic things.

That's an extremely simplistic, sort of childish response. No one besmirches Donald Knuth.

Taking a quote, out of context really, and using it everywhere as some sort of justification, nay, an unthinking reflex, is, indeed, using it as a crutch.