Using demons to do their dirty work is very efficient. They will keep the people needful which is beneficial to the god of life and they will bear the brunt of their hatred. The tree father wouldn't mind hatred if he wanted to be an evil god but being a happy god is a better source of faith.
If there is to be a perfect good god, there has to be an opposite evil to compare with. The god of life will protect the giants of order from the evil demons. So he gets to control the evil and also be the target of all the good. It is eating their cake and having it.
If that is not enough to keep the giants of order faithful, then there are the fragrant flowers in the forest that release special pollens which make giants happy. This happy pollen will work on mana entities and below. It keeps negative emotions and reactions at bay while doing the opposite to positive emotions. It makes it difficult for those living in the forest to become sad and unhappy.
