good vs. bad is situational

Everything that is considered morally good or bad is completely manufactured from what human's wanted it to be. Why is it that helping another person good? Because it benefits them? But what if the benefitting act is executed by someone who is only in it for selfish reasons? Then was the act still considered morally "correct"?
This is what I find the most confusing about good vs. bad and right vs. wrong. Nothing is ever black and white, like we expect them to be. Ever since we were young, we were raised by the notion that doing the right thing is always clear. Not necessarily easy, but obvious, and sometimes rewarding. For example, in the popular story known by kids, Little Red Riding Hood, the hunter must make the decision between killing the wolf or letting the wolf kill Red. In this instance the "right" decision is clear. Kill the wolf. The audience has grown fond of Red, she's a naive little girl who is a likable character, therefor the audience has decided killing the big, mean wolf is morally correct.
What if the story had shifted from revolving around the wolf's point-of-view? Imagine the wolf desperately trying to live off what's left of the forest. There's no more small animals left so she is forced to feed herself and her young by eating a human. She knows the intelligence of humans is quite high so the wolf must trick the first human she encounters. Driven by hunger and desperation, the wolf must kill a little girl. Who is in the right now? The wolf or the hunter?
Good vs. bad is situational and ambiguous. Good and bad is something that is taught at a young age but the empathy to see from the other person's point of view is not.