Final answer:
President Kennedy emphasized US leadership in space to prevent misuse and promote peace.
Explanation:
President Kennedy's motivation for emphasizing that, without America's leadership, space technologies could be used to harm rather than benefit humankind was to ensure that the United States maintains its position as a frontrunner in space exploration and to prevent potential misuse of space capabilities by other countries. Kennedy's goal was to showcase American innovation and technological advancement, positioning the U.S. as the leader in space endeavors, ultimately promoting peace and progress for all humankind.
Learn more about Kennedy's motivation for emphasizing US leadership in space here:
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