Well, no they can't. If you're in the grip of compulsion you can dislike what you're doing, know it's a terrible idea, be fully aware of the negative consequences, but nonetheless be unable to help yourself, in the same way that it's hard for a passenger in a car to exert much control over a dangerous driver. If volition were such a reliable mechanistic thing then we'd have little need for psychiatric hospitals - psychiatrists could just tell mentally ill people what they were doing wrong and call them cured.
I think in this case, the analogy breaks down. Its more that he doesn't see the problem his racist behavior causes, or doesn't have the mental wherewithal to see that it matters.
It's not really fair because neither dynamic has provably defined a correct way of handling social situations/definitions/behavior, because both behaviors often can be traced back to some kind of "reasonable" adaptation or "successful" adaptation which, when not confronted by an equally successful/reasonable force, can become exaggerated,distorted (not necessarily in a bad way).
The problem is some people can explain themselves in a socially acceptable manner, and others can't. People with schizophrenia are some of the least likely to be able to verbalize themselves without the fear perception that it will be taken seriously, equally, diligently - if only from traces of memories of prior experience. People with paranoia have difficulty trusting anything, whether it's the meaning of a word or the person they are talking to. Their minds operate on a different level that is disconnected (not necessarily in a bad way) from people who regularly socially engage with a reasonable level of social connection. If you can't think like a schizophrenic, how can you possibly expect them to be able to communicate themselves in a way that you can empathize with, without them accidentally forcing their own distorted fears onto you?
If you had to question every post you made assuming two worlds exist: one in which the post affects you positively and one in which the post affects you negatively, and you can't tell the difference between either because the possibilities of how reality can manifest are too numerous (or too obvious) to think about, you would constantly be stuck between deleting half your posts and posting things you aren't sure you believe. That's enough to make anyone a little crazy, simply because of the resulting ways that influences your thinking.