You do have proof of this, I suppose? Otherwise your comment reflects very badly on your intellectual honesty.
He might not have been but he was raised by parents who were racist and also supported Hitler.
One recorded fact is that when Sammy Davis Jr. a Kennedy fan, was fixing to marry Mae Britt, Kennedy weighed in on him to put off the marriage until after the election. Kennedy was afraid the news of a black supporter marrying a white woman would lose him votes in the South. Sinatra was so pissed at JFK for this btw that he quit the democrat party and later became a Nixon republican.