The problem is most people see them purely as property and even laws are set that way. I don't think everyone has the right judgement to put down an animal. One thing is extreme suffering and there's a vet that could actually back the person up with real evidence that it was the only thing left to do and a very different thing is kill them just because you felt like it and still get away with it because it's your "property" even if you do it "humanely"
Why you do it makes a whole world of difference.
To me that will always be the last, extreme last resource. I'd try anything before that unless of course the animal is in a lot of suffering and no other way to stop it.
I agree with Golfields
" How we behave toward cats here below determines our status in heaven."
- Robert A. Heinlein