I think you mean Hanlon's razor, but that adage is a farce. Every scoundrel in the world knows the trick of pretending it was all a mistake. Skepticism is warranted.
(There's a reason Hanlon's razor was given that name, I'm pretty sure, and that's because it's not too dissimilar from – essentially it's a much-more-situation-specific subset or variant of – Occam's razor. But I don't think "attribute to stupidity" was what the parent comment was suggesting.)