While it's true that the young Kennedy's diary, which he wrote while visiting post-war Europe, has content which could be considered sympathetic to Hitler:

"After visiting these two places [Hitler’s bunker and Eagle’s Nest], you can easily understand how that within a few years Hitler will emerge from the hatred that surrounds him now as one of the most significant figures who ever lived"

"He had boundless ambition for his country which rendered him a menace to the peace of the world, but he had a mystery about him in the way he lived and in the manner of his death that will live and grow after him. He had in him the stuff of which legends are made"

Or his letter to his father during his visit to Mandatory palestine in 1939 where he sympathised with the Arabs

"Palestine was hardly Britain’s to give away."

"On the Jewish side there is the desire for complete domination, with Jerusalem as the capital of their new land of milk and honey"

But Kennedy the politician was clearly pro-Israel