That Hitler had "issues" is beyond dispute but madman is a dangerously dismissive term used to describe a man who came very close to winning the war.
I hear you, and it is indeed profoundly dangerous to dismiss madmen. Some form of madnesses do not reduce a man’s power to do evil: rather they enhance them.
Hitler was (debatably) a paranoiac monomaniac who ruthlessly gained control of the German War Machine.
His madness made him more dangerous and capable. Whereas if he had believed he was a goldfish, he wouldn’t have been dangerous.
We can see this again today. Ahmadinejad is Hitler’s heir: a genocidal realist, paranoid and monomaniac. Is he safer because he is monomanically focused on destroying the Jews? Is he less able to do evil because he is a ‘magical’ thinker who believes that he is the central figure of Islamic prophecy?
Indeed not. We recognize that both men were less than men in certain ways: e.g. their reduced insight. But they possess (or possessed) the very qualities that make a man dangerous in war - and pitiable in peace.