it's about content promotion. Why should content-promotion algorithms be intelligence agnostic?
Because a "stupid" person might find the same thing interesting as a "dumb" person, hence the upvoting model. People who are inclined to agree are just as inclined to upvote these items, promoting them to a position where other people can consume said content.
And a dumb person may not find the same thing interesting. Do you have any research to indicate one way or the other? If not, why take a position against the notion of intelligence- and personality-based content?
Incidentally, in a sense, that's the old OKCupid model, but instead of LOLcats, it showed you potential relationship partners.
Because a "stupid" person might find the same thing interesting as a "dumb" person, hence the upvoting model. People who are inclined to agree are just as inclined to upvote these items, promoting them to a position where other people can consume said content.