I've gotten to the point where I believe racism is mostly a construct. Racism doesn't actually exist. Many things that are called racism are actually psychoses for example.

Racism does exist, however I will agree half-hardheartedly with your judgement of it being a "psychoses/construct" (technically?) Something people over look/ don't consider is the very biological origins for Racism. Racism, I suspect, originated from psychological fears of differences and the unknown. Racism is essentially discriminating against the foreign, people different to you, with the belief that you (and you're race) is superior. It's a common human reaction, our brains go on alert when something new or unknown is encountered, and so we make our judgement of whether this foreign object/ animal is safe, of value ect. With modern education there is less excuse to be racist, however the initial biological response is most likely what causes the following discriminatory judgement (racism) as it's most likely a coping mechanism for the feelings of unease. This would explain a lot of the superiority complexes involved with racism, (a common coping mechanism used for protecting ones ego) Also I assume racism in modern society is somewhat of a construct a lot of people take on passed down beliefs. Regardless however racism does exist as it's the act of discriminating / holding prejudice towards a race and regardless of why/ where these judgement/ feelings came from you can't just say they don't exist.

I'm looking at it not as a thing like everyone else does, but as a symptom, or better, a syndrome. So there actually aren't any racists. There are only stupid people and psychopaths. Racism is a symptom of stupidity and/or psychopathy.

Not every stupid person is racist, and not every psychopath is racist either. Stupidity isn't a disorder either, unless you meant mental retardation? I don't think Racism can really be described as a "symptom" since it's more a way of thinking than anything else, and generally doesn't indicate any massive underlying problem. What if Einstein was racist? Would he suddenly be considered Stupid? Or would it be more accurate to say his views towards race were somewhat stupid. You can't just racism only occurs in overall stupid individuals or "psychopaths". Racism is illogical (stupid) and fairly un-empathetic (psychopathic??) but not a symptom of those two things. Correlated but not caused.