Evil is evil for many different reasons, it could be because of revenge, because it gives them a place in the world, or because of the money. In some cases it just depends on perspective, that is why...
It means that evil (or whatever other attribute) is defined by actions rather than motives. This statement in question is a philosophical perspective, not hard truth. The above is good, but it also...
maybe. maybe not. it depends on what kinda evil you're talking about. but actually, n general, i think it's ok unless evil picks the fight with you first.