I don't think the quote is wrong, it's just that some things aren't well explained by stupidity. "Oops, we accidentally stole your data and used it" isn't explainable by stupidity but is explainable by malice.
In other words, Hanlon's Razer doesn't say that there is no such thing as malice just that you shouldn't default to assuming malice.
Yes. I'm saying that you should default to assuming malice because in most human endeavors and motives it's the primary factor. Even stupid people can and are evil. The motives I list above cover probably over 90% of human actions. Although that's just my own guess as to percentage, that means hanlon's razor is useful only ten percent of the time.
In other words, Hanlon's Razer doesn't say that there is no such thing as malice just that you shouldn't default to assuming malice.