My best guess is that Onsa is rather loosely adapting the following paragraph of Kennedy's 1963 Civil Rights Address:
We preach freedom around the world, and we mean it, and we cherish our freedom here at home; but are we to say to the world, and, much more importantly, for each other, that this is a land of the free except for the Negroes; that we have no second-class citizens except Negroes; that we have no class or caste system, no ghettos, no master race, except with respect to Negroes?
The "except for..." language used by Onsa roughly matches that used in Kennedy's oration, but that's about as far as it goes. If you have a look at the Japanese version of the address (which, miraculously, exists), you'll find that the sentence structure is not even parallel to Kennedy's. There are also no references to religion in Kennedy's speech, so I'm not really sure what it's doing in Onsa's.
Googling for fragments of Onsa's speech that one would expect to be lifted unaltered from their source (e.g. 「自らの魂のもとに自由」) gets you nothing but Bakuon!! results.
In summary, I'd like to quote one of America's greatest presidents:
"Methinks some intern was crunched for time and ended up passing off random inspirational-sounding quotes as excerpts from Kennedy's speeches."
―Abraham Lincoln