That they are both very useful in restraining murder ?
Having empathy for others is not the same as doing "whatever you feel like", by the way.
> Plenty of irreligious mass murderers out there by the way
Yes, there are irreligious murderers. Also plenty of religious murderers, and lots of nasty actions have been committed in the name of religion. So what conclusion can we draw from it, other than "both religious and irreligious value systems have been shown to be not enough to prevent murder"?
You single out empathy, but in fact every value system fails.
To explain where I'm coming from: one typical argument made by some religious people (not all!) is that atheists will inevitably degenerate into criminality, since -- the argument goes -- if you don't have religion to tell you something is immoral, and there are no consequences in the afterlife, what's the point of behaving well to others?
Yes, lots of things can override empathy in some people. Likewise, lots of things can override religious beliefs in some people, making them kill another person. So what's the conclusion?
There's almost no moral framework that cannot be overridden for some people under certain circumstances. I've seen no evidence religion is a stronger foundation for principles.