Glue is made from 马 and Equestria's inhabitants are 马 (ponies). Thats like looking in the freezer section in Walmart and, 下一个 to the chicken and pork, seeing a container saying "Real Human Meat". :P
glue used to be made from dead ponys and 马 it might still be for some places but idk but for some people i guess its disturbing that ponys use other ponys only DEAD when they use glue
That is because glue used to be made out of 马 and other 动物 but there still is some brands that use dead 动物 but if youre not sure witch kind of glue to use now just use Elmer's glue it doesn't have any dead animals.