I think the point was that he didn't want to argue with it. He was trying to not turn it into an argument of ethics. Besides, as Lentricchia would say, "Tell us truly, have you no filth in your soul?" Most people are not in a position to make arguments of what is and isn't moral. A cynical person that is aware of this will certainly be irritated when they see one.
(For the record, though, his response was a bit on the 'strong' side... lol)
His point was I'm a horrible person. I may or may not be a horrible person. Even if I'm the most unethical person in the world, not sure why that means he shouldn't have to pay sales tax.
I disagree with your quote. Nobody's perfect, if it takes a perfect person to speak up then our board would be filled with empty threads.
He very much did want to talk about ethics. That's why he talks the way he did to try and elicit an emotional response from me.