I have recently come to realize that much of the stupidity on both sides of the political spectrum is due to the same underlying cause: The left dominance of societal discourse. I made this observation in the context of German politics where the Right is basically the AfD (hovering around 10%) which is beyond the pale.
The Left can be remarkably stupid because it controls the conditions and acceptable limits of public discourse. It can get away with obviously wrong statements because „there is no enemy on the left“, i.e. as long as a statements fits the accepted narrative nobody is going to call it out merely for being wrong.
That much is maybe obvious. However, the stupidity on the right is caused by same factor. Because the Right is already vilified for their position on the core issues, there is no additional cost to accepting dumb positions on less important or less political issues. Conversely, all groups that are hated by society at large band together because nobody else will accept them. Therefore the Right will accumulate idiotic positions merely because they are in opposition to the left mainstream.