Why is JFK still so beloved by the Left?

[Peter the Lefty]

      Kennedy did not bring us to the brink of nuclear war.  The Soviets did.  Like Obama, he was political with civil rights.  He did make pro-civil rights statements before it was politically convenient.  He just didn't act on it, since he needed the votes of Southern Dems to pass his social legislation and wanted to avoid pissing them off on civil rights and loosing their votes on the other stuff.  He wanted to wait until he had better Congressional numbers to act on civil rights.  Stupid and cowardly?  Yes.  Unusual in politics?  No.
      His tax cut was nothing like what you'd think of today.  The tax rate the rich paid was 91% beforehand.  He cut it to 70%.  Does that really sound like a trickle-down supply-sider to you?  And the South Vietnamese coup was designed to get rid of Diem.  I can't see why you'd want him to stay.  And yes, he made the mistake of sending military "advisors" to South Vietnam (Johnson was the one who sent ground troops, mind you.). But by the end of his life, he was planning to withdraw them. 
      Yes, his Senate years were pitiful.  And he was slow to recognize the urgency of civil rights.  But these other attacks seem to sound as if you're trying to hate him.

[Peter the Lefty]

I think the bigger question is why it's now so trendy among the left to trash him?

Because he cheated on his wife, was kind of meh on civil rights in the '50s, and other things. 

Yeah... but Johnson is adored...

Adored? No. Revered, maybe. But this lefty doesn't get the Kennedy trashing.

I get the same impression from most leftists; reverence for his substantive accomplishments accompanied with a mixed opinion of the man himself and his broader legacy.

There is some misplaced adoration for Johnson, but I think that's largely a product of there not having been another president who's given those on the left much to be proud of since FDR.

Yeah, we've never had a truly great liberal President.  We've had two whose views basically evolved toward the left while they were in office (FDR and JFK).  And we've had a few lefties who COULD have been INCREDIBLE Presidents (RFK, Humphrey, La Follette, Debs), but of the Presidents we have had, Truman is the only one I would truly classify as liberal from the moment he came to the job.