Lavish wrote Morals are completely subjective so really it depends on the person.

I believe just about everyone except psychopaths can agree that killing someone innocent is immoral, so I don't think your homeless theory works. :p

Yeah, I'm not going to defend the killing of homeless people in their sleep until my dying day.
It's just an interesting question as to why everyone except psychopaths agree that it's wrong.

This makes one think for sure. When it boils down to it though, you are (at the very least) stealing from the person by killing them. That itself is immoral. You are taking their life without their consent. As far as everything else, it would be very hard to argue against it.