Every question you have about Christianity is answered by understanding two things. One: God is an anthropomorphism of the familial bond. Father, son and holy spirit is literally, parent, child, and their emotional bond. It is to your family (and by extension your community and nation) that you are beholden and subservient to. Two: The bible is for a long dead people, in dead language it was for the time and place that they lived. It's like the Oracle from the Matrix, it was telling them what they needed to hear. It can be used as a guide and a reference, but it's not literally the word of God, at least not for you. All your atheist gotchas are invalidated by these two things. How can two opposing armies worship the same God, and fight for him. Well they are of different nations so the God is the same but different. Why did he say to turn the other cheek and love your enemy? There are times and places when this is the right thing to do. The lesson is to be the better man and you'll gain respect. However there is a time and place you need to simply exterminate your enemy.