If we are to be consistent, just like there is no literal god, there is no innate right or wrong.
There are actions, and there are consequences.

In our ancestral environment a hundred thousand years ago, racism wasn’t wrong. It was adaptive. It conferred survivability for our species.

When we began living in large groups of strangers upon whom we had to depend for sustenance, some of our evolved behavioral adaptations became problematic and needed to be modified to enhance cooperation and coordination inside large, complex agrarian societies. Rules were made which curbed some of those problematic behaviors, and myths evolved to culturally enforce the rules.

Racism is still not wrong today. It is an evolved instinct that must be artificially curbed by cultural means if we are to maintain functional civilization.

No behavior is inherently wrong, but many behaviors are problematic if we want to live peacefully in modern societies.
To whatever extent atheists think racism is wrong, they are under the thrall of religious indoctrination. Whatever cultural or individual force is applied to alter evolved instincts, for the purpose of social cohesion, is functioning as a religion, whether true stories or fictitious ones are employed to enforce compliance. Semantic, I realize, but historically accurate.

Compassion for strangers is not natural, automatic, or “right”. If it exists at all, it is because current, local, cultural norms have welded it to the fragment of naturally evolved altruism that we do possess.

Murder, rape, thievery, and xenophobia are natural. Peace, love, and compassion for strangers are super/natural. That is to say, they have been added to our instinctual substrate by cultural means. And for the record, I’m very glad they have. It’s called civilization.

Any preconceptions about another race or gender are stupid and based on nothing. That is why racism must be destroyed in the modern world—many brilliant and most talented people from different races, religions, or genders. I am alarmed by news like calgaryherald.com when politicians make racist statements. After all, a politician is the face of the people, and the people will never say such things about another nation. It is terrible stupidity, and it is very unpleasant that such people still exist.

Racism: prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one's own race is superior.

So reworded: why is thinking one is superior to another based on an inherent, socially constructed trait like race, problematic.

You tell us. If you can. Without exposing your biases and bigotries.

1. Science tells us that we are all so closely related that the idea of race makes no sense.
2. The old rule that if you want to make a moral system, do it as if you were to be at the bottom of the pile.
3. If there are no racial differences then you loose a lot of good people from your list of possible friends by falsely prejudging them, and even if there are races and some were better than others, then the weaker should always be treated with greater humanity. So either way it does not work.
4. Because like religion and god it is a false construct used by people who want to manipulate and profit from others, by lying to them. Every racist needs to ask who is using me.

People are just/only People. Who reor you, or anybody, to tell others they are somehow "wrong"???????

As a younger man I was racist but we can often be racist unawares. Being in the Army helped straighten me out some and over the years I learned more with time. Our earth is a big box of crayons and we that are inside are the colors.

Just last night I watched a very interesting debate on a French TV show (on n'est pas couche). The presenter had invited several black researchers to discuss the status of blacks in contemporary France. In the precedent show one of the chroniclers had made a remark that seem to have been perceived as racist.
This programme reminded me of a reflection about the establishment of Israel, which I call the Palestinian Liberia.
In the French TV show one researcher talked about slavery in France and French colonies. Orignially abolished in 1793 Napoleon restored it 9 years later … and it took another 40 years before it was finally officially abolished in 1848. One of the researchers made a very interesting point: the quest for identity. Slaves did not have family names. He also talked about the stigma attached to the condition of slavery.
He said that usually people refer to their ancestors of renown. Coincidently just before a French singer was asked about one of her great-great-grandfathers: Gustave Eiffel (1832 – 1923). What references can the progeny of slaves use?

It is certainly an advantage if one knows the reasons for one's thinking and beliefs. But all people, at some stage, will just embrace a convention. I prefer someone who is just a Pavlovian non-racist to someone who can explain their racism eloquently.
Racism is not the only -ism we should stay away from, just as we should try to combat types of xenophobia.

Racism causes us (anyone on one side of racism) to dismiss or ignore the humanity, contributions, and potential of those of the "other side". In social structures like the US, it's also a way to create a dominant ruling class that actively denigrates the rights of another group. Without the belief in racism, it's much harder to enforce the social rules about who can live where, or have what job, or why someone deserves to be treated better/worse. To overcome that thinking is such a huge change in thinking, for so many people, that a knee jerk belief in "anti-racism" was needed. Jyst like a knee-jerk belief in racism was required just a few generations ago.

Racism is the negative side of human group instinct and tribalism. I think everybody has a racist impulse, but we should work to consciously counteract or suppress it. The positive side can be ethnic pride, but personally I aspire to see people as just individuals.

Basically a tool to keep us hating each other and ignoring the ones who want to control us, like Nazi or white supremacist, the rich are left alone and control things while we fight each other

You are despicable. I grew up in a family of racists and fascists. I've got to fight against racist thoughts all the time. Racism is wrong because it makes us think that people, yes people, are less than us simply because of the color of our skin when really they're our betters.

I believe that racism is wrong because it is illogical, unscientific, and counter to us being human. Our skins have adapted to climate due to evolution, if we who are pale skinned had not had ancestors who had moved from Africa to more northerly climes, we too would be dark skinned. Basically, what I’m saying is, it is unintelligent and uninformed to be racist. Ignorance of scientific facts causes people to be racist in the same way it causes them to be religious. A combination of both racism and religion is therefore doubly ignorant.

Why? Because "race" is a null concept. All humans are the same race or species. Our common ancestor, approximately 200,000 years ago, was dark-skinned. Any genetic variation since then in skin pigmentation is simply natural selection for climate regions after the migrations out of Africa. It has nothing whatsoever to do with character, intellect, or the host of attributes with which skin color has been wrongly associated in popular legend and prejudice.

You might just as well say that Trump is an idiot due to his white skin, and Obama is a genius because he's black. But that observation, again, is completely unscientific. Skin color is completely unconnected to anything else. There is no such thing as "race" other than as a cultural construct.

That is why racism is wrong, from a scientific point of view. It's provable. As an atheist, that's what I care about.

As a human being, what I care about is that racists (on all sides) are dreadful people who do dreadful things and then try to justify themselves by saying, "Well, why is racism really so wrong, anyway?" You should be fucking ashamed of yourself.

I think you're trying to say the belief that racism is wrong is just dogma? If you believe the Humanists tenents are correct then you try to believe and live the fact that racism is wrong. We probably all are guilty of some form of racism. But we learn from those experiences.