Contemporary leftists have a bad habit of treating people like FDR and JFK as if they were gay liberationists. However, according to leftist Hegelian thought, the TVA and Peace Corps were the "gay liberation" of their day, and if FDR or JFK were around today they'd be in the forefront of the perversion lobby. And considering the number of fossilized leftists who promote this stuff (or are silent about it), I can't say that they're wrong.
Bobby Kennedy was part of an anti-Communist Democrat administration, but as soon as Nixon took the White House the Democrats who put us in Vietnam immediately morphed into hippies opposed to the "Republican" war.
This movie also recalls the old days when (in America at least) support for Israel was the "liberal" position. RFK was a pro-Israel liberal assassinated by an Arab terrorist for that very reason. This movie is just what Jewish liberal Democrats need to keep living in the past.
Well, of course in their own day, they weren't. But John Kennedy -- at least in part -- followed the Harvard consensus of his day, and he'd follow that consensus where it went -- though maybe not on all issues. JFK wasn't entirely a liberal in his own time. He certainly wasn't a gay liberationist. But if he were still alive today, I doubt he'd be a part of the Christian Coalition or the Moral Majority.
Moreover, Democratic ex-presidents and ex-presidential candidates, do tend to go left in retirement. At least Carter did. It's the same phenomenon that drives television ex-anchormen like Walter Cranked further left.
The things that kept JFK more conservative than some other Democrats in politics (his Irish background, Catholic distrust of liberal Protestants and Protestant liberals, his father, etc.) wouldn't have been as strong a force on him had he lived out his term.
Kennedy wouldn't have been a liberal saint had he been reelected -- Vietnam and Cuba separated him from his liberal critics -- but out of office he would have done what he could to satisfy the liberal establishment, because as with Carter or Clinton, they'd be the curators of his reputation and the people he interacted with most.