I'm going to suppose that your reference point is the "We Must Free Ourselves" speech given by John Lewis in 1963 at the March on Washington. The simple answer to the question is that Lewis did not think President Kennedy and the federal government had given genuine support to the civil rights movement. Lewis was even forced by the Kennedy administration to edit his speech because the initial draft was so strongly critical of the administration. Let me quote you a section from the draft of the speech that Lewis was pressured to drop before actually giving the speech.
Mr. Kennedy is trying to take the revolution out of the street and put it in the courts. Listen, Mr. Kennedy, listen, Mr. congressman, listen fellow citizens, the black masses are on the march for jobs and freedom, and we must say to the politicians that there won’t be a “cooling-off” period. We won’t stop now.
In the speech which Lewis did give, he pointed criticism at JFK in a less direct way, saying that the party of Kennedy was the also the party of Eastland. James Eastland was a Democratic senator from Mississippi who was staunchly opposed to the civil rights movement.
John Lewis called on black citizens to stand up for their own rights, because the political leaders could not (and some would not) do so for them.
