Earlier quoted context omitted.
> Why would it matter if there is no life after this one? If there is no life after this one, maybe you should just "get over it". Because for as long as we are capable of caring, we should care that other people have to live with the consequences of our actions.
> we should care... But that's my question: if there is no afterlife, why?
The answers so far are a little snark, however this topic has been debated for a long time and most of the pro/cons can be listed rather easily.