Selling knives might not be evil, but that doesn't imply that there's no level of weaponry that would be immoral to sell. Would selling fully automatic rifles be evil? What about chemical weapons, or nuclear bombs? The question is where to draw the line, which is subjective, but I'd argue that most people would draw the line _somewhere_, and I don't think it's as clear-cut as you're trying to imply where stuff like auotmated surveillance software falls.