The reaction that nationalistic leaders, specifically Malcolm X, evoked from both Black and White America is very interesting. White Americans, for the most part, were frightened of some of the statements and beliefs that Malcolm X articulated. Calling White Americans "the blue eyed devil," or statements like Kennedy's death was an example of White Americans' "chickens coming home to roost," might have been more rhetoric, but went far in solidifying his image as one that was more concerned with resistance and striking an according stance as opposed to working with the White establishment in making them feel better about the issue of Civil Rights. While there were some White Americans who fully understood the point of view from which Malcolm X was coming, many Americans were scared of what was being argued. Black Americans had a more complex reaction, in my mind, to Malcolm X. Some Black Americans were in complete agreeement with what Malcolm X was saying. Brother Malcolm spoke from a disenfranchised and abused point of view, a position that resonated with many Black Americans of the time period. Other Black Americans felt that leaders like Malcolm X were great at the rhetoric and talking about the issue of Civil Rights, but in the face of lynchings and physical abuse in the South, other leaders like Dr. King were actually doing something about it such as protesting and standing in the front lines and taking the heat of what was being offered.
First of all, not all white or black Americans reacted in the same way to the fact that Malcolm X was Muslim. I would say that the difference in how his religion was perceived was based more on age and political beliefs than on race.
Both whites and blacks with traditional values were skeptical of Malcolm's religion. You have to remember that the Christian church was (and is) an extremely strong institution in black communities. Therefore, someone who moved away from Christianity would seem suspect in the eyes of traditional blacks just as much as it would seem wrong to traditional whites.
To me, the major racial difference in perceptions of Malcolm X were based on his racial ideas. Whites generally reacted badly to Macolm's ideas of black nationalism and his idea that whites were evil. Blacks were more receptive to these ideas because they had had to endure so much abuse from whites over the years.