ScoobyDoo
NPC
I'd say they're more misinformed than actually dumb, and sadly it's a global epidemic. My wife and I have witnessed Thai youth moving to the right, we saw Duterte elected here, Germany has moved to the right, Macron in September unveiled a new government dominated by conservatives and centrists, there's been a right shift in Italy, Finland, Greece, etc., and there's more at play here than the average human becoming less intelligent.
Dumb, misinformed, ignorant. All synonyms in my eye.