Did you read what he said? Hardly leftist. Liberal, in a classic sense, yes.
No, he’s a leftist. The fact that he has this one opinion that isn’t pro-authoritarian doesn’t change his being far-left.
Leftists make lofty statements all the time - it’s what politicians do that defines them.
The Kennedys were dirty Democrats - don’t start quoting dead Kennedys and expect patriots to hero-worship martyrs of the left.
If you want to know which path the assassinated Kennedy brothers would have chosen, just study the political legacy of the brother that wasn’t assassinated.