This is not an easy thread to reply to, but I'll try.
Racism is not an inherent trait, it is learned in one's youth and over time from family associates, and where/when you live.
I grew up in a household with Christians and Jews, many of them my "family". Our neighborhood was mixed with Whites, Jews, and Asians - my best friend was sent to a camp during WII. The local racism was against "beaners", Mexicans who lived in a separate neighborhood nearby.
In high school, I tended to associate with whites but did have some "colored" friends, although I still tended to feel ill at ease around Mexicans.
I entered the army and encountered my first truly racist group of people - my platoon had 32 men assigned to it and only two of us were not from the Deep South. One thing I saw during my three years there was the anti-blacks changing their bias to against the French and becoming friendlier with fellow soldiers who were black.
Over the next 23 years in the military, my views towards race mellowed and I had some very close friends of all races and backgrounds. Some of the finest men I served with and under came from racists I had once heard to be inferior. Those who spouted hateful, racist comments soon became outsiders and some slowly began to change their viewpoints due to close encounters. I may be wrong but think I lost any racism over that 23 years.
When I retired and moved to Las Vegas, I can honestly say I no longer had any stupid racist viewpoints. And then, after a while, I got a job driving the city bus. There was one route through the "ghetto" and I actually enjoyed driving it. No problems whatsoever. However, black drivers hated it. When I asked, I was told it was due to their fellow blacks always asking for a break in the form of a free ride. Giving one would cost a driver his or her job.
I then drove a taxi and quickly learned some calls I dreaded - always "welfare blacks" who wanted me to do everything for them, sneered at me as being racists, and never left a tip. I met and married a Mexican girl 24 years ago and my entire view of her people has drastically changed. I've gained a feeling of pride in their history and their beliefs.
So, what do you say to a racist?
Nothing!
The only way to change racist viewpoints is by his or her getting to know and understand those they are racist or bigoted against. As we learned in the army, one doesn't give a damn about the skin color of the guy in the foxhole with you.
I hope that makes sense and gives you an idea or two.