[Eldar14]

Gothmog, you raise a very good point regarding how there are lions in captivity which don't attack their keepers. However, this isn't because the lions are tame.

In most cases of a predatory animal being kept in activity, such as in zoos or circuses, the zookeeper plays a very clever game to convince the creature that the keeper is dominant, and that the keeper is more powerful than the predator. There have been cases where once this illusion is broken the lion will kill the keeper.

For example, one way this happens from time to time is if a new creature is introduced, and this animal doesn't yet know the keepers position, it may attack the keeper. The instant this happens, and the keeper shows their weekness, the other animals also attack.

So, while there often is an illusion of tameness amongst naturally violent animals, this is merely an illusion created by the animal's fear and respect for its keeper. The parrallel for orcs in regard to this phenomenon wouldn't be an orc growing up in society and fitting in, but the fact that an orc doesn't attack his superiors because he believes them to be stronger.

It's not that the lion is tame to its keeper, but that it believes its keeper is more powerful.