You did not "speculate" about anything. You labelled a belief as crazy

I argued that it was congnitively inefficient.

that seemed to be based on scientific facts, was supported by scientific authorities, and has only very recently fallen into disfavour

Ermm..it's not based on current science though. Are you trying to say that the cognitive error of racism is not what i said it was, but rather that it was merely based on outdated science? I do wish you guys would drop the dog whistle and say what you mean.

If you'd lived about 50 years ago, you'd say the same about the belief that ethnicity has little or no impact on intelligence/aggression/sociality/whatever and any such perceived differences must be the result of cultural differences, communication problems, and selective evidence.

Whereas it has a slight impact. Maybe. But that gets back to what I was saying originally. Racism treats unimportant factors as important. That;s the bias that's going on here.

ETA:

And here's someone (edit: someone ELSE) self-daignosing what I was saying:-

As someone from the southern US, I was asked (jokingly) about whether or not I was a racist when I went north for college. At first I was repulsed by the question, until I noticed that I automatically got more nervous when passing a black person on the street at night. I am going to college in Cleveland, and so I have some actual reason for this since every mugger I've seen for five years in incident reports has been black. My problem (though I only started defining it this way within the past few months of reading LW) is that I was weighting race far too strongly in my everyday interactions.

After I realized I was doing this, I decided to switch my threat assessment style to a more clothing-based approach, with some success. Everyday interactions with other races than my native white within the university also felt easier and less forced. Taking an implicit association test helped me to realize that I was racist to some degree despite my intense repulsion to the idea. I now encourage everyone to examine their thought process for racism, especially if they would feel dismay if someone accused them of racism.