"War will exist until that distant day when the conscientious objector enjoys the same reputation and prestige that the warrior does today."
Is it a good line? Sure. Did Kennedy think it up? No. Did he even express it as well as the one from whom it was taken? Nope.
He just dumbed down this brilliant line from Gibbon:
"As long as mankind shall continue to bestow more liberal praise on their destroyers than on their benefactors, The thirst of military glory will forever be the vice of the most exalted characters."
As an aside, do I believe in Intellectual Property? Nope. I don't think the Kennedys owe the Gibbon estate money, I just think everyone should read Decline and Fall before they buy a paperback of Profiles in Courage.