Children can't give consent. As to animals, on an emotional level many people are married to their pets, as to sex, as distasteful as I find it there seems to be little point in drawing a moral line between killing and eating something and / or having sex with it. As a meat eater I don't feel that a sheep is 'murdered' for my lamb chops, so how could I be offended by its 'rape'?
I guess they can do what they want in private. I just believe that they will have to answer for their actions someday.