It pisses me off when people are abusive towards animals. But let's consider this story by replacing the cat with a human. 7 yo cat = 49 yo aduly male. Now imagine this 49yo guy walking up to your porch every night and taking a poopy there. Fire is extreme, but I'd forcibly push him off and threaten him and then set up some sort of fenc or pitfall to ward him off.
If a person does it, I'd beat the stuffing out of him, then throw him on the street. Animals are one thing, grown adults are another.
Exception: mentally disabled individuals, in which case, I'd beat up the person's caretaker for being negligent. :3I like how it leaves no trace of evidence. Civilized & cool.
Now if you could just ask a Jedi for a loan...