There is no doubt that he was a very talented composer, but considering that he lived in a time when racism was prevalent, one might imagine the general public had varying opinions about him.
Did the fact that he was black affect the way people viewed his music?
Joplin's music was viewed as pop thrash at best and lewd and primitive at worst. Ragtime was closely associated with prostitution in the public's mind. It was the music of brothels and gamblers. Joplin did in fact work as a pianist in brothels as well as private clubs and bars. After the success of Joplin's best selling piano rags he was able to live a modestly comfortable life for a few years. He tried to stage two operas, which failed. He moved to New York thinking he would have better luck attracting funding for his more serious works, but was unsuccessful in staging them. He was also going insane and had trouble playing the piano due to syphilis, which eventually killed him in 1917, just as the ragtime fad was beginning to be usurped by jazz. Joplin's tale is heartbreaking. He was a genius working in a genre that wasn't yet taken seriously and era that wasn't ready to recognize an African-American musical genius. I strongly urge you to read Edward Berlin's book, The King of Ragtime: Scott Joplin and His Era (Oxford University Press, 1994) to learn about his life and how ragtime was viewed during his life.