They aren't. Without Republicans, gay marriage rights wouldn't have become a thing. With out Republicans, segregation wouldn't have ended. Women wouldn't have the right to vote if it wasn't for Republicans.
None of these rights that people have would have happened, if it wasn't for Republican voters too.
If all of these topics hit the voting cycles & every republican tried to keep them from happening, they wouldn't have happened.
But - there are republicans who aren't Bigots, there ARE democrats that are Christians too. Every thing isn't black and white like your post suggests.