Movies should cast the best actor for the part — whatever their race or gender. Sadly many viewers are race-conscious rather than race-blind.
Diversity is important for movies. The whole world watches Hollywood movies, and our films should include a great variety of talented actors, regardless of race or gender. Traditionally, American television and movies have been less than stellar at casting people of color or women for parts that could be portrayed by any ethnicity or gender. The raunchy comedy South Park, even shamelessly goes after this trend in television and movies by having one African American character who is named “Token”.
If a new movie is released and it isn’t based on older movies, or history, then Hollywood should strive to bring more diversity to their cast. For example, take a science fiction movie like Edge of Tomorrow. The film takes place in the future and involves battles between humans and aliens. Hollywood can and should cast a diverse team for these original movies, as it’s new territory not built on past franchises.
The real diversity that matters — whether in schools, work, sports, or movies — is intellectual (performance), not racial.