Yes, those of us who prefer Hillary to Donald have often certainly implied, if not outright declared, that those who think Donald is the better choice are "stupid" or otherwise "not quite right in the head". Here is the problem, though. I politely suggest that if, repeat if, a person unashamedly embraces a candidate who is clearly a crackpot, that person is literally begging to have their mental faculties challenged. And - and this is really important - it appears that the more nutty Mr. Trump acts, the more his defenders like him.
No wonder the sanity of the Trump supporters is questioned - it's not so much that he is supported, it is that he is lionized for his wacky statements and actions. This is what has us shaking our collective heads.
Now you may be very well be one of those Trump supporters who thinks he is better choice even though he is clearly an immature narcissist who is not remotely qualified. Fair enough; at least there is a case to be made here.
I would also question the mental powers of any who would somehow think that Hillary is the better candidate because she is dishonest. This is the problem: it certainly appears that many, although certainly not all, Trump supporters inhabit a 'bizarro-Jerry" world where things like infantile behavior, race-baiting, and misogyny are actually virtues. By contrast, I think the Clinton crowd acknowledge she has moral issues and understand this as a weakness, not a strength.