The appeal that Martin Luther King Jr. used in this line from his "I Have a Dream" speech is: Pathos.
Pathos is an appeal to the emotions of the audience.
In the given lines that were called from Martin Luther King's speech, we see that he was mainly encouraging the people to move into action and end racial injustice. He was appealing to their sense of justice.
So, pathos was employed here.
Learn more about pathos here:
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