Who is the guy in forrest gump wearing the american flag shirt at the vietnam rally?

The man wearing the American Flag t-shirt is supposed to be Abbie Hoffman; the actor who portrayed him was Richard D'Alessandro (born on May 11, 1960 in Massapequa, Long Island, New York).

Hoffman was the leader of the Youth International Party (Yippies); a self described "child of the Woodstock nation", and "an orphan of America."

He was born in Worcester, Massachusetts on November 30, 1936, and became involved in the Yippie movement around 1966. In 1974 he avoided trial on drug charges by changing his name to Barry Freed, and undergoing plastic surgery. He was arrested well over 3 dozen times over his life.

On April 12, 1989 Hoffman was found dead of an apparent suicide at his home in New Hope, Pennsylvania.

State Supreme Court justice Gustin Reichbach was an anti-war advocate that helped defend Abbie Hoffman in the 1960s; he passed away on July 15, 2012 after a lengthy battle with pancreatic cancer.