How exactly did Kerry or anyone else "aid the enemy"? By using one too many bullets in killing enemy soldiers? Perhaps it was by going after several enemy soldiers single-handedly instead of waiting for backup and risking them getting away. . .
You probably mean that because they second-guess the orders they followed to the letters after having time for common sense to trickle into their grey matter against the wall of brainwashing built up in training. This is somehow treasonous? Oh please - that's rich.
Want to know how to tell a veteran from a recruit? The recruits parrot the brainwashing they've received in basic about how great it'd be to go "into action" and are generally gung-ho about the missions, the orders, the weaponry and equipment, etc. The veterans are far more reserved since they know the reality and the truth of what warfare is. Those still in service try to get through it with their heads still attached to their bodies and those out of service generally seem to express reluctance to discuss their service - if not outright dismay over it. Why do you think that is? 'cause war is so great?
Constantly questioning the legitimacy and authority of our government and holding it accountable for tyrannical actions is a patriotic duty - not a treasonous act. It's a responsibility we are charged with as citizens of this nation - directly from the founding fathers themselves.
I'll bet they'd be horribly ashamed of what the U.S. government has come to mean, be and stand for. . .