The person above wasn't making a reasoned persuasive argument, they were making a moral assertion. The purpose wasn't to insult someone nor to convince them. It was just an expression of moral outrage.
The commenter I replied to seemed to unaware how far they had strayed beyond reasonable ethical statements. I don't think I could persuade them to change their position but I couldn't let that go unchallenged. Norms change one person at a time and speaking out is important.