Can you reason your way to become one of the Good guys?
Or is the best it can do is stop you getting caught or getting you off the hook?
I think the foundation of any morality is a set of somewhat arbitrary precepts that define the underlying values on which a given set of moral judgements are based - a hierarchy of importance, as it were.
As a rough approximation, for instance, I'd put forth the ideas of personal freedom, growth and safety for everyone as the foundation for my morality, and everything builds from there. Other people will, no doubt, have a slightly or significantly different balance, but they've all got an underlying set of presumptions or assumptions influenced by their background, culture, education, upbringing and personal experience that they use as their own personal foundation.
You can discuss with others why you have the set you have, perhaps you can even convince someone to change their opinion on some of them, but I think they form organically in most people without much conscious or deliberate thought, and most people probably don't examine them in any detail in the course of their lives.
O.
