believing God has intimate relations with endless wives
This is symbolic of the deep intimacy God has with each of us; not to be taken literally. Of course, if you hang out with ISKCON Vaisnavas, they may indeed take such symbols literally.
Well, the descriptions of the different planets definitely seems very literal. Last thing I read about it was something about Radha being Krishna's main consort and doing something horrible to another one because she got too close to him.
That was probably one of the main tipping points where they started looking like demons.
Similar to the way that the Church Fathers re-interpreted -- in the Light of Christ -- the Old Testament texts concerning Israelites killing Canaanites, many Hindus also re-interpret texts that speak about violence and other morally reprehensible activities, in the Light of the higher teachings of Krishna, Rama, Ramakrishna, etc.