As a matter of fact he is not following his own words. If he punishes a cat he is not treating it as a cat but as a human. A human who has killed another human feels guilty and will never forget it. So if he is punished he knows why and (maybe) learns that he should show a different behavior.

A cat who killed a flower jar never will know that it did something that is not socially acceptable. It is just cat behavior without any knowledge what the jar costs and that water is bad for the carpet and that means punishment - especially later, when you come home- will not have any effect at all. Cat simply has forgotten all about it and does not understand why he's punished. And of course he won't learn and can't learn from it. So it's just senseless cruelty to him.

We all know that if we want to discourage a cat from a certain behavior it only works on the spot (as you know very well from Luna ).

So if he'd really understand the differences between cats and humans he wouldn't talk that stupid stuff.