This is a point that shouldn't be difficult but it appears that it is. Andrew McCarthy in the Wall Street Journal essentially accusing lawyers who represent terrorism suspects of treason --
The nation is at war, and the detainees are unprivileged alien enemy combatants. By contrast, the United States was not at war with England at the time of the Boston Massacre, and the British soldiers were lawful police, not nonuniformed terrorists.
This refers to the opponents of the treason argument using the fact that John Adams represented British troops who had shot civilians in Boston, a deeply unpopular move at the time.
That time being 1770. And there's the problem. If your argument is that there's no precedent for American lawyers representing the other side at a time of war, then your refutation can't involve a scenario where the United States of America was not at war ... when there was no United States of America!
The Adams case was a British Crown prosecution through powers of the colony of Massachussetts, whose governor feared that he wouldn't be able to find any defence lawyer for the troops accused of murder since the local sentiment was inclined to see the troops as the enemy and their defenders as collaborators. Which is pretty much what the right is now trying to whip against GWOT defence lawyers.