That may be true. I tend to see moral issues in strict terms of black and white. I can't help it. It's just how I feel.
I've read quite a bit, but I'd say I'm far from being an expert. This is just my own personal gut feeling (although based on some limited degree of personal observation too).
I would have had sympathy before they acted out. That for me is completely negated when they do. And I realize you're not talking about justifications or excuses, but for me there is a direct correlation there.
No, I'm not really expecting them to make rational decisions. But, why must their rationale be understandable by our terms. Your cats were very likely just playing, or thought the tree looked better lying down. By this I mean just because we don't understand their reasons doesn't suggest that they don't have their own totally rational reasons for what they do. Sorry, but I still believe they are completely capable of moral choices and see no reason to believe otherwise. I think we may just have to agree to disagree on this one man.