Intelligence can be defined in many ways, but yes, I find a large majority of ATRL members to be pretty stupid. Part of that might be the fact that many users are still in high school or younger, and part of it might be that the culture of ATRL kind of makes acting "stupid" kind of acceptable and even funny, since the main reason most people are on this site is for some sort of entertainment. But there are definitely many users that seem to be very intelligent, at least objectively, and I'm sure many others are intelligent in other ways that clearly aren't expressed on ATRL.
I think most of us realize that talking about our favorite celebrities and getting into "stan wars" is just a silly pastime. ATRL doesn't represent any specific intelligence level.
although I don't use that site as much anymore 