Mine is the volume of their voice. If all that they can do is just talk too loudly with no reason for it and don’t control the volume of their voice. That to me is a sign that you’re a stupid fuck. Because people think the louder they are, the more righteous and attention seeking they are. Than it is to just listen, digest and respond accordingly to anyone talking around you.
Religion of any type.
I’m less certain. Lots of intelligent people can get caught up in such things. Religion depends also on upbringing and cultural background.
This. One of the smartest guys I know, running a worldwide software business, is religious. Faith does not equal stupid.
Agreed, faith can often be a sense of comfort, not necessarily gullibility.
Blanket elitism about atheism, or rather blatant anti-theism, is one of mine.