if I understand correctly, Buddhism is opposed to dualistic concepts: Us vs. them, beautiful vs. ugly, pain vs. pleasure. We should rather realise the emptiness of those constructs in order to see the things in the way they really are, i.e. see their real nature.
How then, does that translate to the concept of good and bad? Because I think every Buddhist tradition teaches us that certain behaviours, acts or ways of thinking are beneficial and create good karma, whereas others are detrimental to our spiritual progress or to our own well-being and that of others and create bad karma. Examples of good vs. bad behaviour abound in many texts like the Vinaya rules but also in the Noble Eightfold Path itself. Right speech for example is considered good whereas the opposite - lying, denouncing, spreading rumors, careless speech in general are surely to be considered bad, detrimental, whatever you want to call it.
How can I accept the duality of good vs. bad while accepting that other dualities are just hollow projections of the untrained layman's mind that keep me from seeing the true nature of things?
I would also be greatly interested if somebody could shed a light on the different traditions' views on the subject.