As I see it 'good' and 'bad' are just social constructs. We attach the label 'good' to things, people, goals we as a society like and 'bad' to things, people, goals we don't like.
A bigger problem we've got today is that people have, broadly speaking, stopped thinking about morality at all - i.e. the question of 'what is good' or 'what is bad' hardly occurs to people (that is ethical questions), rather they are concerned with aesthetic issues (e.g. most of the food and photo bloggers on here) or with practical questions (what's the most efficient way I can maximize my return'.
So while I think you're right in what you say, and that 'good' and 'bad' are ultimately relative (which relates to Sartre's ideas about 'monstrous freedom') - the sadder reality is that most people don't even consider ethical issues.
Or to put it another way:
- Most people don't think about ethics (issues of good and bad)
- A minority think ethically, but in a sort of dogmatic way and so just get into conflict with other people with a different set of values.
- A tiny, tiny minority, having realized that ethics are relative start to think about the question (which IMO is the sociological question of days, following Zygmunt Bauman) of how we can live ethically (because it is necessary) in a postmodern age....
NB - This kind of thinking doesn't have a happy ending... Nietzsche (who wrote 'beyond good and evil' which I think is one of the earliest books that basically says ethics are totally relative) went mad, Sartre who followed on from him just seems to have ended up being miserable and gradually more and more contradicted, Foucault whose a later incarnation of these two (sort of) died of AIDS as a result of his 'freedom ethics' (sort of)....
I think I started off making some kind of profound point then just ended up rambling, anyway... Zygmunt Bauman is an interesting character to check out on postmodern morality.
Enjoy!