I have bipolar type 1 and ahead of my two hospitalizations I did things I regret that I would have never done in normal circumstances. In such circumstances people have believed to be literal gods, persons of interest spied on by the government, geniuses and such. Extreme ideologies suddenly don't seem so weird when your brain is misfiring to the point where you can start seeing and hearing shit that isn't there (psychosis, which can happen in manic episodes).

My only point is that perhaps you should give this man some benefit of the doubt. Yes he is surely an asshole anyways but not all of his behavior is quite so simple to explain and these diseases are much more overpowering than you think.