If you want to hold onto irrational biases, that's your business. You are only harming yourself. However, if you try to spread your prejudice to others, then you are spreading the harm you do to yourself to others minds, which can then escalate to actual harm to those who are the target of the prejudice via group egregore/tribalism. Be mindful of what your contribute to the tribal egregore.
I agree with
@crossfire here, and I am glad to see several other posters put up similar lines of thought.
It's really not about you, but about how you effect others around you.
Racism from the get go is simply and undeniably wrong. To blanket a vast number of people with your (usually negative) preconceptions, based upon nothing more than the pitiful small n-value sample size of the few you have interacted with, is moronically childish and wrong.
If you cling to your delusion and keep it to yourself, then you will only hurt yourself by missing many opportunities in many aspects of life, all the way from love, to money.
But unfortunately we can almost never avoid spreading our hateful delusions to others around us. You
will form a group of like-minded delusional people around you. I'm not saying you will open a chapter of the KKK, but rather I speak of the people that you will form friendships with (of course only those filtered through your racism), the person you choose as a spouse, and your children. Some will be drawn in, but sadder yet are those you convince, and these may be your own or even other people's children.
As a group, you will reinforce each other and make your racist delusion seem like well reasoned thought, with each member bringing their pitiful few horror story examples as more evidence of your righteousness.
It is the self-supporting (self-deluding) self-righteous group that (when large enough) can bring about the horrors depicted in
@Quagmire's post #9, or even start the self-fulfilling cyclical racism, by spreading out into society, with the resulting years and generations of lost opportunities for people of your blanketed 'underclass'.
Or
Or you can get real, and educate yourself
@The Ardent Atheist. You can realize that all humans are just humans. Each is as capable of terrible evil and self-serving, as they are of kindness and brilliance.
It is the actions of the individual that you can judge, rather than taking the lazy and foolish route of mass judgements. I have known blacks who were smart, wonderful personalities, doctors, artists, and scientists, and I have had black punks in my face itching for a fight. But I can say all those things about Native Americans; and whites; and latinos; and south east Asians; and Indians. (Actually , I've never met an Indian "itching for a fight"
).
Regardless, you won't (as you already haven't) be able to keep it to yourself. You will affect others directly or indirectly. And your deluding yourself to boot.
Now don't run out and give the pusher on the corner a big hug and sloppy kiss, but don't give the smiling black 4-year old, or your black doctor a dirty look either.
wow [\rant]