I've recently encountered racism from someone actually capable of thinking. In the event there are more like him out there, and even in the event that some harboring racist tendencies are capable of thinking but don't tend to apply that process to their racial reactions, I'd like to point out fallacies that racism entails. This is primarily centered on racism geared toward Blacks in the United States but has applications elsewhere.
I'm going to start in a strange place: what racist assumptions would mean if they were accurate. They aren't, but I'll get to that later. Racist assumptions are, at heart, generalizations. They can go in all sorts of directions. Here's an example:
"Blacks are more athletic than Whites."
If this were true, there would be no White guys in the NFL. So, what's really going on here?
When dealing with human beings, the differences between populations are in averages, in the central tendencies of aggregates, not in individuals. If you were to say "porpoises are more intelligent than sharks," you would mean that all porpoises are more intelligent than all sharks; in other words, that the stupidest porpoise was smarter than the smartest shark. This is clearly not true of people - see the NFL example above for an illustration of how this logic doesn't work - but this thinking is at the heart of most racism.
If you were to graph this, the racist assumption is that you'd have two completely separate (or nearly so) blobs on a graph. What you'd actually get, again, even if racist data about phenomena such as differences in IQ were accurate (which they aren't), is a pair of bell curves with slightly displaced centers such that the curves overlapped almost completely. What are the ramifications of this?
Let's say two randomly selected individuals were applying for the same job, one Black, one White. Let's say that the aggregate data showed a 20% difference in median IQ's of these two populations (which would be a huge difference), a 60/40 split in percentiles of medians. Such a split would mean that, in 40% of cases like this one, the Black applicant would have a higher IQ than the White applicant. This isn't the result racists had in mind. It also isn't enough of a result to affect employment or promotion because employers have no reason to gamble against such bad odds; there are too many variables that are way more reliable (like employment history, grades, etc.). The same is true of, say, college admissions officers faced with an analogous situation - there are too many far more reliable variables available to bother with this one.
In other words, if such data were accurate (keeping in mind that my numbers are fictitious though the existence of data along these lines isn't), they'd be functionally useless because they'd be insufficiently predictive of individual results. It wouldn't help to even know about them unless we were going to use them for, say, a study on nutritional differences to see if that accounted for a piece of the result with remediation in mind. (Given differences in average poverty levels, this could in theory be an issue.)
However, the data aren't accurate. They can't be, because they can't be measured, at least not on the genetic basis that those who introduce such data have in mind. Why not? Because our sample is, from a genetic standpoint, too mixed. How exactly do we define Black when measuring anything comparative?
Generally speaking, we're looking at a population that self-defines. Based on what? Mainly, given the lack of a genetic definition, appearance. What appearance tells us more than anything else is how members of the sample population are likely to be treated, taking the probable cause of observed statistical differences out of the realm of the genetic and into the realm of the environmental. Racism is, first and foremost, a genetically defined phenomenon: "They are born inferior." Because of the issue of defining the population, the existing data suggest just the opposite: that statistical differences between racially defined populations are not based on differences in capabilities determined by genetics but on environmental conditions. (In the case of Blacks, by forced environmental conditions.)
Even if we didn't have this genetic definition issue, the evidence still wouldn't point toward racism making sense on this basis. Why not?
Given that we know that there are a lot of statistical differences between Blacks and Whites (collectively, not individually, which is a critical distinction), the first question to address from the standpoint of addressing racism is whether these differences are genetically based. If we were to theorize that these differences are environmental, which is to say the cumulative result of abominable treatment, how would we test that? By finding a Control Group. A control group is a group from the same population that hasn't gone throught the same treatment.
If the genetics are the same
and treatment is different
but the results are:
...the same, a genetic cause is likely. (If we could define one in the first place.)
...different, treatment is the likely cause.
As it stands, we do have a control group: Blacks who immigrated more recently from the West Indies (Carribean) and their descendants. In other words, Blacks in America who are not descended from slaves and didn't go through generations of Jim Crow. What do we know about that population? They have:
A higher median income than American median (not American Black median, American median, Period),
A higher median education level than American median, and
A lower median crime rate tha American median.
To use a well-known example: Colin Powell belongs to this group.
We can be pretty sure that African ancestry per se isn't genetically responsible for statistical differences in aggregate results.
Biologists could tell you this without bothering with a control group. From a biological standpoint, race is a thoroughly insignificant variable when it comes to comparative capabilities. However, as of yet, racists don't seem to be taking biologists' word for this.
Why is this an important distinction? Because abominable treatment, unlike genetics (at the moment, and this isn't a can of worms I want to get into), is fixable.
Not all discussions of racism center around the genetic, regardless of the assumptions behind them. Some are about "cultural" factors. Culturally manifested racism isn't legitimate either, but that's another discussion.