lol, in my experience there is definitely some truth to this. I met a lot of stoners at college, and most of them were dumbfucks who were just obsessed with talking about weed and having pseudo-intellectual conversations about spiritual experiences. Then again, not all stoners are these types, so I tend to smoke with people who are an exception to the rule.
~50% of the population is of below average intelligence, and average intelligence is pretty bad. Pot, like some other stimulants, merely lowers expression inhibitions. In short, yes, it illuminates the "dumb fuck".
Not overused, pot can also stimulate creativity and introspection in the other 50%.
I hate those stoners that turn into zombies that don't talk anymore, most of my stoner friends are like this. Then you have the types that descend into conspiracy theories and can't stop ranting about chemtrails.
Lately (as of the past year) I've taken a liking to smoking joints by myself and just listening to tunes in the dark or watching Star Trek tbh. I still greatly enjoy social smoking but I've opened up to smoking by myself. It's nice quiet time.
Some folks, myself included, also shut down on certain strains because of paranoia. People misunderstand paranoia, they think it's worrying about the police coming. It's not. It's about thinking all your friends are secretly out to get you and everyone's actually making fun of you with inside jokes you can't comprehend.
I leave when it's that kind of high, but when I can't, I tend to go zombie.