It is misleading to say that Hinduism is about the worship of gods.
Much of the worship in Hinduism is directed towards demons, i.e., spirit beings who are amoral or immoral.
Kali is one of the most popular Hindu demons - she wears a garland of skulls, human fetus earrings, and demands child sacrifices.
Worshipping Kali is essentially the equivalent of worshipping Satan.
All of this is hidden from non-Hindus, who think that Hinduism is essentially about Chicken Tikka Masala, synchronous dancing, and throwing colored power in the air on Holi.