There is one benefit from it, though: a much larger market of gluten-free products than would exist if the only people buying them were people who legitimately suffer from celiac. In that respect it's a net positive: stupid people are out some money, but it's hard to get too worked up about that since (being stupid) they would have probably found some other pointless thing to waste it on anyway, and at least this way their waste makes it possible for celiac sufferers to have a better quality of life.

The only hitch is that fads are by their nature transitory, so at some point the stupid people will flit away from gluten-free to some other fad, and the market of gluten-free products will collapse. Which will kind of suck for those who actually need them.