admitting to war crimes. This is a historical fact. When Kerry, a former Navy officer, testified to widespread war crimes before the Senate, the effect of his testimony on the POWs was devastating. His words were used to undermine the POWs resistance. Some of these men had been in captivity for over 5 years when Kerry testified.

General Giap wrote in this autobiography that the war would've ended years earlier except for the support given by the anti-war protesters. The North Vietnamese held on because they saw the antiwar protests as the source of their victory.

“…if it were not for the disunity created by...stateside protests, Hanoi would have ultimately surrendered.”

As the war dragged on, thousands more people on both sides died. In no small measure, the protesters (including Kerry) gave aid and comfort to the enemy. There's a word for that.

Source.