This is a news article on a award-winning documentary that highlights the contribution of African-American scientists, especially during the period of World War II. Many of these scientists either never got the credit they deserve, or it came later. It is also rather painful to read the kinds of treatment they had to endure, even when what they did was vital to the war effort and the security of the nation.
I suppose even today, while it is no longer as blatant and as bad as it was during the period covered in the documentary, there are still issues surrounding the fair treatment of minorities and women in the sciences. My personal take on this is that in terms of one becoming a physicist, the issue of race is no longer there. The small group that I work in has such a diverse ethnic, racial, and national composition. We have scientists/engineers/students from the US (of course), China, Brazil, Russia, Malaysia, and Lebanon. And for most students and faculty members in physics, it is highly common to have students from all over the world in the classes and in research projects. So in physics and other sciences, I would hazard a guess that one tends to have more contacts with people from various parts of the world than in most other areas (unless of course one works in some international relations vocation). So scientists, in general, I would think would be more familiar with other nationalities, and the issues of someone being different is usually not a big issue.
What could be a big issue is in the promotion of people into upper management and decision-making position. The question on whether there are enough minorities and women in tenured positions at well-known schools have always been an issue being discussed continually. A former Harvard president even "lost" his job recently for a rather flippant remark made about why there are fewer women in the sciences. So this issue certainly hasn't gone away.