As I person who would most likely be considered ODD by today's standards, this is what I have to say on the matter:
"I'm not arguing, I'm simply stating why I am right."
I'd be interested to know how many great minds would be considered ODD. Or how about lawyers. I've yet to meet a lawyer that doesn't love to argue impulsively! it's a gut reaction to start with "no." And when I studied philosophy, it was a prerequisite for almost every student.
To innovate, to create, you must be free of the limits. You must break and destroy to build. I find it curious that the ODD diagnosis says that while we all show "symptoms" of ODD, what makes a person ODD is their extreme quick impulsive No to AUTHORITY.
I say, "i'm not arguing, I'm simply stating why I am right."
Maybe your son will grow up to be a brilliant lawyer. All I know is that I enjoy directing my energy towards arguing (as I am doing in this response), as does my oldest and hubby. While I want to strangle my daughter because of this, I think it's a sign of a super active and critical mind. The world needs more critical minds, not more people submitting to authority. Some argue that mental illness is merely a natural response to impossible demands for sensitive minds ( RD Laing, Foucault), and by labeling them as illness we fail to see their magic (look up all the research on manic depression and genius, for instance).
Instead of seeing this as a negative, turn it on its head and help him channel his criticality towards something constructive and productive. Has he found his "thing?" If not, help him find his thing to direct this powerful, creative energy towards. It is a powerful creative energy J.B. it's the very spark that lights fires of creation. yes, it is destructive, yes it questions authority, but it is the very stuff of creation.