Well, that's probably more complex than you might have anticipated. At least that's what I thought at the time.
He could've gone to Canada, he clearly had no desire for actual combat with an enemy. He could've claimed religious dispute but he professed none at the time. He could've joined something other than an elitist unit that was immune from combat duty. He could've exempted himself from political intervention and prevented himself from jumping ahead of hundreds that had been placed on the roles before him. He could've protested an unfair and unrighteous war that was being propagated by individuals that professed otherwise. There are lots of things that he "could've" done but his choice was to avoid duty to America and his choice was duty unto himself. Maybe that's the American Way that I misunderstand. And that is what so many other Americans also fail to fully comprehend, IMHO.