Here's Campbell's "testimony" at the VVAW's 1971 Winter Soldier investigation.
My testimony will consist of eyewitnessing and participating in the calling in of artillery on undefended villages, mutilation of bodies, killing of civilians, mistreatment of civilians, mistreatment of prisoners and indiscriminate use of artillery, harassment and interdiction fire.
So he was with Kerry and watched Kerry and his ilk do do all of these things and he also participated. Sounds like they are war criminals to me...