I understood them to not so much mean stupid in the clinical sort of sense, but instead the proudly ignorant sort of stupid. I’ve met a ton of conservatives and most of trump supporting type is in a bubble and actively avoids learning anything that they don’t agree with. They form an opinion and then only look for supporting evidence. Critical thinkers instead look for information from various sources and then form an opinion based on the varied evidence. People who still support trump are not critical thinkers, or they know who he is and like that he attacks and blames the people that they want getting attacked and blamed. There’s a reason he attracts hate groups, casual racists, and evangelicals. These people are also ignorant, but also pretty cunning about it.

But memes are bad at nuance, so they just said “stupid” as a general shorthand. At least that’s what my take is.