I don’t believe that a persons use of profane language can be used reliably to judge their intelligence - or indeed lack of. I know situations can arise where profanity is used as a reason to dismiss an individual and/or their cause. I like to think i am in better/less judgemental company here…
I grew up in a fishing port and some of the most (and least) intelligent people work in that industry. You cant judge them by conventional means, they all swear like troopers.
You might see one almost blind drunk, cursing and fighting with anyone who comes near. But the next night he’s in his bunk reading stuff like Homer’s Odyssey or Paradise Lost (he lent me that, way too deep imo).
It also comes down to nationality. In the UK swearing is not solely preserved for the lowest social classes. I have worked on some fancy floating gin palaces in my day and most of the owners love to swear their heads off. Especially when they know their wives cant hear them.
I think some of the best people to know are argumentative tossers with social issues, myself included 