Great ethical dilemma - especially after waking up at 6:00 to find all my uni classes being cancelled. Hopefully I'm awake enough to make sense.
Anyway, I believe in moral relativism and utilitarianism.
Meta-ethical moral relativism states that there is no universal right or wrong. Utilitarianism states that the best course of action is that which will maximise benefit (AKA utlity).
As a sort of combination of the two, I believe that the vast majority of ethics, notions of righteousness and evil, and even systems of morality, have all grown out of what people believed represented utilitarianism for their societies - whether in the 1st century Middle-East, or 21st century Europe.
So I believe Krishna was wrong in his statement that (his notions of) "righteousness" should be unquestionably accepted. He was also wrong in going further and claiming that this "righteousness" should be fought for regardless of the cost.
As a non-Hindu, I'd even go as far as saying this story is ironic. The whole system of ethics (and even characters like Krishna) where made for the solepurpose of encouraging people to form a society that maximises utility (benefit) for the people. Yet here, Krishna is encouraging Arjuna to ignore these utilitarian foundations and fight for principles that might now be obsolete, or understood to be plain wrong.
Obviously, I don't believe that the principle of not cheating is wrong, but like all ethics and morals, it should just be questioned under a framework of ultilitarianism. I don't quite know what benefits or suffering would be cause by the cheating Kauravas ruling the kingdom, but if all the fighting involved in getting the rightful Pandavas onto throne causes more pain and suffering, then IMO the right thing to do would be to just let the Kauravas rule.