@Ryan

If I were to decide that what was beneficial to the human species was to eliminate all non-beneficial members of society (i.e. mentally and physically ill, old, and homeless people among others) and go around murdering them all, how would you be able to tell me I was wrong? Because you felt empathy for those people? What if I said that I overcame my empathy to aid the human species, because those people only held others back and I was doing others a favour by ridding them of useless people. What would you say to that?

EDIT: You said that feeling empathy and ignoring it makes people evil, but what is that opinion/belief founded on? Why do think it is that that makes a person evil instead of something else? Suppose I think that good and evil is determined by someone's willingness to do what is good for society as a whole and suppose that was killing off the baby boomers because people were held back by caring for them and too many working hands were wasted on them instead of doing something that would benefit society in the long run. Who would you be to say that the way I determined right from wrong was incorrect while the way you did so was?