It is because it's a bee product, but also because of the way bees are harmed in the process. Of course, in harvesting veggies/grains/etc some insects are harmed, but in the process of honey harvesting, usually some bees are killed and many see honey as less necessary than veggies/grains/etc. Also, especially in big honey-production companies, they remove all the honey, royal jelly, etc and substitute much inferior products for the bees to use (as honey is the food of bees). Some of these big outfits also kill the queen after a couple of seasons (as it's easier just to buy a new queen and start over), some even destroy their hives after every season (as moving them to warmer climates costs a lot)--sometimes by burning the hives, some behead the male bees to get bee "sperm" to inseminate the queens, etc.