You would have to provide a better and more precise definition of "stupid" then, the word has a tendency to become circular
Perhaps you could use the word "idiot" and refer to them as "idiots". The term has been used in a medico-legal context in the past to define a person's mental age.
That there is a divide between the two parties and the average intellectual ability of their supporters is a well-known fact. I'd contest that this is less of an issue than their racism.
So you really think more than half of the Americans are mentally impaired? The probability of being mentally impaired is higher for a random poster like you than for half of American people.
Your understanding of statistics is deplorable. Also, your reading ability. I specifically said it's racism, rather than the (verifiable) lack of intelligence.
True, "stupid" is a very imprecise term. But my main point was merely that epistemically, there is no validity to something just because a majority is behind it.