Because calling someone a racist is a tool used to distract from the discussion. If I point at you in a crowd and scream racist, sexist or any other term loud enough...there are enough people who will follow the masses like sheep and simply believe it. They won't listen to your argument on the merits anymore. And why would the race hustlers stop doing this when it's quite effective as a political strategy ???
And unfortunately there is an extreme double standard in American culture. Take the recent incident with the NBA owner Donald Sterling. I am not going to defend his opinion. But he is entitled to have it, and was not trying to make it public. He is now a man blacklisted by the NBA for expressing his views in a private conversation. He is now demonized and hated as a racist, and engulfed in a lawsuit forcing him to sell his team. Yet the same NBA employs Spike Lee on NBA radio...who has made more than his share of racist statements...quite publicly...and very recently before Mr. Sterling's comments.
Racism is a portrayed as a one way street, even though it isn't...and is quite an effective political tool. When all else fails accuse someone of an "ism" of some sort. Eric Holder recently suggested that part of the opposition to President Obama was race driven. Yet, he was elected by predominately white voters twice. Now if I point out that more than 95% of Blacks voted for Obama..does that imply they are racists for disagreeing with Romney in the last election and voting against a white candidate in such disproportionate numbers. Even if I came to that conclusion...nobody really cares. It doesn't quite sell very well does it.
Has anybody noticed that the majority of the border patrol agents are themselves Hispanic. Yet they and their union have been very vocal about this problem. Are they self hating bigots ???