I think the quote is misused. Narcissistic self interest is neither incompetence nor malice. It's something else entirely.

It's malice. Nobody ever sees themselves as the bad guy. They always have some rationalization of why what they're doing is justified.

I'm not bad, I only did $bad_thing to teach you a lesson!

	▲	gtowey 11 hours ago \| parent [-]
		Which brings up what IMHO should be the main takeaway from this: The first requirement to fall into this trap is to believe you can't fall into this trap. It's still possible to do malicious things even when you believe to your very core that you're not a malicious person. The only way to avoid it is a healthy habit of critical self-reflection. Be the first to question your own motives and actions.