If "Sky Daddy" is the literal creator of the Earth who gave direct commands to mankind, then that alone is a pretty valid reason.
If he isn't, then he's a powerful (yet imaginary) social construct that has evolved over the past 4,000 years to encode the wisdom of many past generations through a set of rules and stories that happen to match up with the stories and rules of many other cultures. It's also an incredibly fast and low-cost way to reach a solution.
Either way, there's definitely some validity to the claims of any major religion.
I'm not sure these views are as consistent as you say they are.
The Atlantic slave trade started in the 1500s and ended in the 1800s. Even then, it was controversial and faces opposition from certain Church groups (while getting support from others).
Vilification of gays based on Christian religious grounds apparently goes back to the 11th century (based on a quick read of Wikipedia, TBF), and is only starting to come undone now. I don't really have an answer for this, it was unfortunate.
