SMG--
Verily, JFK was an ardent and active global anti-communist. That JFK might make adjustments in his Vietnam anti-communist policies and strategies is hardly a reason for anyone to assassinate JFK.
JFK's acceding to a plot to stage a US-financed coup against the Diems remains a blot on his record, especially as he was warned the coup would likely be lethal, and could destabilize SV, which it did.
Nevertheless, read JFK statements why he created (or revivified) the Green Beret and USAID. All about fighting global communism. Why did JFK risk a nuke war over Cuba? To keep communism out of the New World.
The leftists have tried to re-frame JFK as singing kumbaya with Castro and Khrushchev, and holding hands with Muslim dictatorships and despots, but it is all demented hagiography.
RFK was assassinated for being an Israel-backer.