Depends on the type of racism. If it's a false sense of superiority - probably the most common type of racism - well, maybe. But if it's the belief that some type of people are hostile to you for some reason, and your personality makes it so that you return it, then it is a persecutory delusion, just like conspiracy theories.
I grew up with a diverse group of friends, we used every slur under the sun to shit talk eachother and still do when being idiots. Those slurs have no meaning to us beyond the comedic value they provide in their vulgarity. I'd be shocked to discover any of us were racist, pretty strange to have not noticed after >20 years.
Schizophrenia (and other related disorders) can induce in some people obsessive socially unacceptable thoughts, which can include racist thoughts. It doesn't happen to everyone with schizophrenia – there are plenty of people with schizophrenia who aren't racist. And even if a person with schizophrenia is racist, it isn't necessarily due to their schizophrenia – they could well be racist for the same reasons many people without schizophrenia are racist. But that said, there absolutely are some people who aren't racist, and then they have a psychotic episode, and as a result of that psychotic episode they develop racist delusions/obsessions.
This can take the form of persecutory delusions, but not always. Schizophrenic delusions can take make many forms other than just persecutory, so in some people schizophrenia can induce non-persecutory racist delusions.
As for socially unacceptable thoughts, yeah what yesterday was acceptable is today unacceptable. :)
It is possible, that without schizophrenia, he would never have been racist. (At least if we define "racism" in terms of explicit statements/actions, as opposed to unconscious biases.)
It is possible that he always was racist, and would have been even without schizophrenia, but schizophrenia took away his ability to hide it from others, or made him not care about doing that.
Nobody can really know.
This is how society works to make progress, yes.