As a non jw who went to Sunday school I can assure you that mainstream churches do NOT have children reading about masturbation, death and violence. Our Bible stories were simple and age appropriate. If you are of a certain age perhaps you remember Golden Books? they were simple cute books for children, they put out a number of children's bible stories. We also often did singing and a craft or coloring in Sunday school. In mainstream churches they do not discuss sex, masturbation, oral, anal and whatever else the perverts like to discuss with children and in mixed company (once upon a time such topics were not discussed in front of men & women together).
I can't even imagine sitting in church with my Dad or Grandparents when such topics would be brought up! It is just one of the many reasons I never allowed my kids anywhere near a kh. Told my jw that if anyone ever tried to have a discussion like what jw's do in their 'service' I would beat the shit out of the speaker.
Before I get roasted for that, when discussing the above topic with other non jw's they all agree they would do the same. I don't know, are jw's just a bunch of perverts or what?