This is a spot where I have years of first-hand experience, and those claiming that Kanye West's mental illness has absolutely no effect on his views - he is actually just an evil person - are just flat out wrong. We can get into why they are wrong later, but the first thing you need to know is that they have no idea what they are talking about.
DeBoer's points are quite good. They desire greatly to go straight to good vs. evil rather than anything complicated. "Complicated" as in "above fifth grade level", doncha know. They may think they are being nice to mentally ill people in some way. I don't know that for certain, but let us grant that they have a sort of framing that says "There are evil racist people in the world. Mentally ill people get picked on and blamed for lots of things, but they are all fine, really. So they can't be part of that evil racist group, or if they are, they got there completely independently of their illness." These are indeed convenient rather than scientific beliefs. It would be better for their ascension to power if this were true, therefore it is true, because it is clearly a good thing that they ascend to power.
It is hard to imagine what such people believe the effect of mental illness on thinking is. If paranoia does not impact one's politics, if impulsivity does not affect one's approach, if grandiosity does not change one's perceptions, if anxiety has nothing to do with ones' cultural beliefs, then what, exactly, does it do? When people are manic they feel much the same as antisocial personality disorders, and i have many times heard line staff declare "Yeah, when we get his affect under control I'll bet we find that he's also go ASP going on as well," only to find that the patient in question is sweet and engaging when treated, with no hint of a personality disorder.
At a much smaller level, if you are over-caffeinated are you more likely to say something unpleasant to a person who irritates you? Are you in fact likely to find more people , and more types of people, irritating at all? How about when taking depressants, like oh, I don't know, alcohol?
It is almost a cliche for family or friends to be tolerant or forgiving of those with mental illness who are offending them and ruining aspects of their lives to say "I know that's not him. That's the illness talking." In fact, those who are claiming to understand these conditions so well have it exactly backwards. The problem is that very decent people find themselves doing indecent things, which they are ashamed and humiliated about later. To insist that one can only say offensive things if that is part of one's core personality is to make such sufferers feel even worse. They now dare not ever be in a situation where they might encounter you when ill, because you will judge them to be bigots or promiscuous or violent or whatever.
I will guess that what is actually going on is that West absolutely destroys their definition of what a "white supremacist" is, and they have to defend this rather than reality.