Any word that seems to evoke an emotional response can be considered a charged word. JFK uses many rhetorical devices, but these planned "charged" words directly address the various audiences to whom he speaks.
To the allies, after the war and in the midst of a cold war, he uses the words "united" and "divided" in different sentences each of these demonstrate that there is no middle ground and they must proceed together for the interests of all. This attempts to generate unity.
To mankind, particularly Americankind, he notes the power we possess. He uses our ability to "abolish" and gives it two different connotations. It could be used positively if we exercise human compassion and abolish "poverty", or negatively if we extinguish "human life".
He repeatedly uses freedom, pledge, liberty, and revolution. Each of these words have stood the test of time for American patriots and they evoke a sense of national pride as well as favor in humankind.
He also uses citizens and mankind to evoke a sense of unity among Americans and among peoples worldwide. His message is one of cooperation and he works to ensure their buy-in with this type of language.