I do believe in the right - and the virtue - of Hayden's visit and Fonda's later on, but I always questioned the wisdom.
Making a statement about personal freedom of travel and communication and fact-finding on the part of ordinary citizens is important in its own right but the actions did impede progress toward ending the war by being needlessly polarizing to the people they needed to reach most: mainstream Americans who supported the war.
'We refuse to be anti-Communist' is not a good statement to make to people who have sons or neighbors dying to (supposedly) prevent the Communists from taking over South Viet Nam. An SDS radical (especially in stogy old 1965) was too easily accused of bringing aid and comfort to the enemy.
I'm sorry. Good intentions on the part of the anti-war left in the '60s did not temper the damage done to the effort to end the war.
In retrospect, the confrontational politics practiced by a sincere but naive left were instrumental in the election of Richard Nixon in 1968.
Hayden's trip is not as well publicized as Fonda's, of course, but it is hard to remember one without the other.
I believe that the photographs of Fonda manning an anti-aircraft gun in Hanoi hurt the cause she was trying to promote.
Hayden's, too, but to a lessor extent. Whatever they hoped to accomplished was swamped by their own celebrity.
Somebody else should have made that visit.