Is masturbation healthy or harmful?
Very healthy and natural. Just look at all of the other species closest to us genetically, for one thing.
It is the church that condemns masturbation. One book I read strongly suggests the reason is to instill guilt, for which forgiveness is only offered through the religion. Self-perpetuating cycle that keeps people dependent on the church.
And just look at all the sexual problems at churches that pop up in the news.