Me personally, I have to wonder. If you don't recognize blanent messages of racism in a TV show, would you recognize them in real life or be just as oblivious?
Remember that in 1968, cities were on fire because of racial tension. Rather than take such a volatile subject on directly, Star Trek addressed it indirectly. It only works if people recognize the connection, of course. Those who didn't recognize the negative results of discrimination in 1969 had to be living with their heads buried in the sand. You didn't need a TV show to illustrate it; the Nightly News did an excellent job.