An ODD diagnosis for an adult is totally different than for a child. An ODD adult is permenantly angry and often violent. Its people who get into bar fights, its people have emotional meltdowns several times a day, its people who road rage incidents, its people who decide to fight with the police.
Nick in public exhibits none of the symptoms that would lead to an ODD diagnosis in an adult.
Nick or doctor could be trying to do a childhood ODD diagnosis on him. But that is effectively saying that Nick has the mentality of a nine year old and is rebelling in his 40s against his parents.
Like alcoholics usually do, Nick reaches for everything to justify his drinking. He has claimed it was OOD. He has claimed that because he is a lawyer, he is doomed to have it. And on and on and on.