In a nut shell I would describe "bad" as something hurtful to either yourself or others. Yes well ,we could then debate what is "hurtful" couldn't we ? Ah well symantics!
Everything you do / think is not OK in my opinion - it is not that simple if it hurts others. I had a moments flash of thought rejection the other day while listening when it made it sound like anything was OK and my thought was of my father-in- law and what he did was not OK - and yet he still tries to justify it all. He would love to have someone tell him it is really all OK 
You're right, many do manifest "evil" or "bad"
Hitler hurt others.
Sexual abuse of another hurts others while giving satisfaction to the perp.
etc.
Lisa
