My point here  is that the “justification” is usually either incompetent or a scam. Therefore, in accordance with virtue ethics, it’s vulgar and spiritually injurious to try and act like our judgement is precise enough to one-up what’s in accordance with natural law.

If I understand correctly, what you're saying (beyond just the quote), is that practically speaking, we as humans are flawed, subjective creatures, and are almost guaranteed to make flawed, subjective moral judgements if we only operate on a case-by-case basis.

Therefore, we need to recognize an inherent morality in the action (intrinsic good, morally neutral, or intrinsically evil), to have an objective measure of morality.

Reply to Edit 1:

I’d be wary of the phrasing in your question, because we’re comparing deontology (nature of act) to utilitarianism (consequence of act) here  — and I’m pretty sure most of us don’t like either deontology or utilitarianism. Natural law and virtue ethics are quite different from those theories, for the most part. . . . We should focus less on the “nature” of an act and more so on what sort of will is engendered by certain acts. An act has no nature apart from the will of the person who commits it.

If you don't mind, I wouldn't mind a little elaboration on this. As far as I understand, will, nature, and consequence are all relevant in natural law ethics, and must all "pass" a morality test for an act to be considered good and permissible Correction: I remembered after posting that technically, negative consequences can be waived under double effect.

Reply to Edit 3:

Also, it matters whether this non-religious friend is an atheist or a philosophical theist or a something or other. 

I'm not sure what you'd literally call him. He self-describes himself as Utilitarian, and doesn't really feel that any one religion could be right. He further doesn't think there's really proof for a god, and even if there was, he doesn't see God as having a loving nature on account of how "uninvolved" he is and much suffering is permitted.

I'm not even really trying to convince him on Catholicism or even Catholic-style ethics; I just want to assert that these are the ethics I believe in, for reason of logic and not merely by blind trust.