I've heard that when Clinton's letter to the ROTC Colonel surfaced, while Stephanopolous wrung his hands and reconsidered the seminary, Carville smiled and said, "This letter is your best friend."
Kerry needs to approach his 1971 Senate testimony in the same way. He was a returning soldier who had seen his friends maimed and killed for a war that was being administered very badly by the civilian leadership. He was driven by both passion and principle and he is driven by those same qualities today as he sees another generation of young people, many the same age as his own children, killed and maimed as an incompetent administration refuses to admit it has made a single mistake.
Contrary to those with a political agenda who want to distort his record of service with valor as well as his words in opposition to the war, Kerry never claimed to have seen soldiers engage in the worst of the atrocities he mentioned. But he had heard them testify that they had done so "at times."
Contrary to critics who say he slandered the vets he served with, he was chosen by many of them to speak for them in their opposition to how Washington politicians waged a war for more than ten years that they never had a feasible plan to win. His passion may have led to stronger language at times than he would use now as a more mature statesman than he used as a twenty-something Vet returning from Viet Nam, but his passion for the truth and for taking proper care of our troops in battle and our vets after they return burns just as strong.
Now, as then, John Kerry sees an administration that has stumbled badly and our nation's bravest young people are paying the price. Now, as then, John Kerry sees an administration that has acted arrogantly and has alienated much of the world. Now, as then, John Kerry is ready to fight based on principle and to insists that no one who joins our military will have their commitment to this country result in them being placed in harms way unless it is absolutely necessary.
Don't back away, don't apologize, don't cede the moral high ground, don't let them define your defining moment up till now.