Why is it in the history of civil rights movements, do some leaders (e.g. W.E.B. DuBois, Booker T. Washington, Martin Luther King, Malcolm X)...

I do not know of any specific examples of any of the people mentioned in the question referring to others as "Uncle Toms," but these men are certainly representative of the diversity of opinion among African-American political leaders at both the turn of the century (when DuBois and Washington had their disagreement) and the 1960s (when King and Malcolm X had theirs). DuBois' chief complaint about Washington was that his "accommodationist" strategy--accepting social discrimination in...

I do not know of any specific examples of any of the people mentioned in the question referring to others as "Uncle Toms," but these men are certainly representative of the diversity of opinion among African-American political leaders at both the turn of the century (when DuBois and Washington had their disagreement) and the 1960s (when King and Malcolm X had theirs). DuBois' chief complaint about Washington was that his "accommodationist" strategy--accepting social discrimination in return for economic equality in the South--would not lead to real progress for African-Americans. Washington, on the other hand, thought that without economic progress, blacks would continue to be marginalized in every way that mattered in the United States. As for Malcolm X and Martin Luther King, the former deemed King's strategy of nonviolence in search of political reform insufficient, though he did not really promote violence as is commonly believed. He also believed that King's message of racial cooperation was naive, and advocated African-American solidarity in the face of racial injustice. Other groups, like the young civil rights workers of the Student Nonviolent Coordinating Committee (SNCC) resented King's perceived control of the movement (many SNCC activists mockingly called him "de Lawd"). Robert Williams of Monroe, North Carolina, argued for "armed self-defense" in addition to nonviolent protest. Even King himself moved toward increasingly radical, fundamental social change in the years before his death. All of the above were skeptical of the legalistic approach taken by the NAACP. Ultimately, the movement for civil rights in the twentieth century was very complex, involving interaction between national leaders (who usually get the credit) and hundreds of thousands of local people (who are usually forgotten). Naturally such a multi-faceted movement would involve the kinds of disagreements referenced in the question.