He may well have seen another thread where someone did actually recommend these as fish food. No doubt carrots are fine for omnivores and herbivores; I was very surprised to see bread recommended though, I would not think that is a good idea.
you asked this exact same question on another message board....
why are you feeding your betta bread and carrots? bread isn't a vegetable, btw. why do you want to feed a carnivorous fish vegetables anyway? is he constipated?