Animals are pure and uncorrupted in their nature, which is why many people feel it is uncalled for and horrible when bad things happen to them. Man is corrupted and "self-aware" or perceptually aware, meaning that when he does "good" or "Bad", he is knowledgeable of the two and makes a choice. This choice is what corrupts man, because choice isn't always right, but truly "right" is in the eye of the beholder. It's easier to answer this with an example.

Scenario: A small kitten is casually walking down the street when a human comes by and steps on it without reason and kills it.

Scenario: A small human is casually walking down the street when another human comes by and steps on it without reason, and kills it.

I feel the same sympathy, though the man who killed the other man will be held to the standard of taking away an intelligent life versus just destroying a creature. I probably am not answering this correctly, but I'm at work and scatterbrained. I see no difference, though I cry more for the innocent animals versus the corrupted non-innocent humans. But in either of the above scenarios I would fight to defend the creature in question, regardless of a cat or human.