In the Port Huron Statement (1962), the Black Panthers' Ten-Point Program (1966), and Cesar Chavez's "Letter from Delano" (1969), are the authors' arguments persuasive? Why or why not?

Whether or not the arguments made in these documents are persuasive depends, of course, on the individual. In answering this question for each document, one would have to consider the sources and the broader context in which each was produced. In the case of the Port Huron Statement, for example, the group of young men and women who produced the document were essentially arguing that the United States, once a great nation, was now betraying its origins by its militaristic behavior in the Cold War, the "permeating and victimizing fact of human degradation" that was Jim Crow in the South, and other aspects of American life in the early 1960s. The authors cite many examples in addition to these.
The Black Panthers' Ten Point Program is a series of measures demanded by the Panthers to improve the lives of African American people, especially those in the cities. These include a program for "full employment," financial reparations, armed policing of predominately black communities by black men, and new trials for African American men and women convicted of crimes. Again, this document has to be considered in its context. The Black Panthers were a particularly militant, if influential, wing of the movement for civil rights, one born out of the injustices of inner-city life. Evaluating the persuasiveness of their claims involves a thorough study of the conditions that they were responding to with the Ten Point Program.
Finally, Cesar Chavez's "Letter from Delano" is a response to accusations by grape producers that he and his followers provoked violence through their strikes and protests against working conditions faced by migrant farm workers. He evokes both Gandhi and Martin Luther King Jr. to emphasize that their protests have been nonviolent and that it is the agribusiness leaders who have provoked the violence. More to the point, like King's "Letter From Birmingham Jail," he refuses to back down from his strategy of nonviolent direct action. To evaluate the persuasiveness of this document, it would make sense to look at the facts of the strikes, assessing whether Chavez and his followers were indeed innocent of the violence that sometimes broke out at their protests in the late 1960s.
https://history.hanover.edu/courses/excerpts/111huron.html

https://libraries.ucsd.edu/farmworkermovement/essays/essays/Letter%20From%20Delano.pdf

https://www.marxists.org/history/usa/workers/black-panthers/1966/10/15.htm