Given that Robert Kennedy was killed in 1968, and Kerry was still in Viet Nam in 1969, I doubt Kennedy specifically meant Kerry.
Americans who commit treason nowadays are guilty by words given long before they were born. Does the definition not apply? I think this is one of the things liberals today attempt to do today; create situational ethics. Anything is right or wrong, only depending on the situation and circumstance. In their view, treason only applies to whom they choose.
Kennedy outlined the mold Kerry fit into, period. Kerry gave aid, comfort and encouragement to Ho Chi Minh, by a Kennedy's own words.
Let fat Ted suck on that for a while.