If I told you of a dog breeder who excelled at training his dogs and did so by killing those that didn't do as he wants, what would you think of this guy? What if I told you that his favorite trick to teach his dogs was to beg? Everywhere he went in his dog enclosure the dogs must bow; any dog that didn't, he took that dog and threw it alive into the furnace in his house's basement.
Early in this guy's career things weren't going as he'd mistakenly thought they would, so, in a tantrum, he threw almost all the dogs — adults and puppies alike — into his swimming pool to drown. Then he started over again with just the few that were his favorites. Even now, from time to time, he kills off large numbers of his dogs on little more than a whim, and sometimes he'll slowly torture a dog to death as a lesson to the other dogs to fear him.
What would you think of someone who praises this guy as a great man and a leader in his field? What would you think if they tried to convince you that torturing dogs, burning dogs alive and teaching them to constantly beg proved that he loved them?
If some people have told him that what he's doing is evil and immoral, but he insists that as a dog-breeder, the dogs are his to do with however he wants, what do you think of the accusations and his excuse?
Thankfully, that dog breeder doesn't exist. He is the fictional god of the Bible and some other religions.
Can you see why spreading belief in such a god promotes evil?