Although Thurgood Marshall and Martin Luther King, Jr., agreed that integration was a central goal of the civil rights movement, they did not agree on the methods of achieving it. [[Proofreader: Commas around Jr. OK per MLA style.]]

Civil rights leaders Thurgood Marshall and Martin Luther King, Jr., were similar in many ways, but they had their differences too.

The first sentence expresses a focused idea that can be developed in a paper. The other sentence is too vague to be an effective thesis.