He was a snitch in Hanoi.
I think he had the capability of being a snitch. Could have been one in Hanoi, may have been one in the Keating Five scandal, and definitely was one when he handed the dossier over to Comey.
In most instances, if you became aware of unverified dirt about a fellow Republican, and knew that it could possibly be detrimental, not only to the person and his family, but to the party, and country as a whole, the normal thing would have been to contact that Republican first, and advise him about what you had discovered. It shouldn't matter if bad words has passed between you, because in the end, the goal should be to look out for each other, the party, and the country. You'd think that type of loyalty would have been drilled into McCain's head as a Navy pilot. But McCain is only loyal to one person, and that is himself. Instead, he deliberately went out of his way, to procure a copy of the dossier for himself, which he probably read, and then handed over to the Comey. McCain, being the bitter p*ick he is, deliberately sought out a copy of the dossier as a means to attack and harm Trump. McCain didn't care about Trump's wife, or his family. And he certainly didn't care about the Republican Party, or the country for that matter. He had one desire only, and that was to put the screws to Donald Trump, no matter who or what it ended up hurting.