I decided to read my bible because it had been a "best seller" for hundreds of years. I wanted to know what was in it that made it so popular. Like you, it seemed to me there were inconsistencies and contradictions. At times I wanted to throw my bible against the wall in frustration. I kept studying the bible and over time I started to read with some understanding (I still have much to understand). It's a pretty amazing book when that happens. Below I wrote my interpretation of the quote you cited. (Doesn't mean I'm right- it's just some thoughts of mine.)
But as for these enemies of mine, who did not want me to reign over them, bring them here and slaughter them before me.’”
Your above quote is from a story Jesus told about "end" times when he would come back and judge the world.
A gunman walks into a school and shoots several people and we wonder where is the justice in that act? There is justice in the world. It will come at the end times. Most christians are happy to know that ours is a just God and there is justice in the world. He is a just God, but he is also a merciful God willing to forgive.
Last sunday my minister spoke on the story of the prodigal son. The rich man in the story had 2 sons. Both sons had free will. One son chose to stay with the father. The prodigal son left taking what his father had to give him and squandering it. After he had squandered everything so that he had nothing left the prodigal son decided that even his father's servants were living better than he was so he chose to humble himself and come before his father and ask if he might be a servant. When the father saw him returning he ran to his son and hugged him. He threw a big celebration at the return of his son. The other son was miffed. He chose not to celebrate the return of his brother. It didn't seem fair that he, who had stayed and toiled for his father, should go to the party his father threw in celebration of the prodigal son's return. He did not want to forgive his brother. He felt that he was more special because of his loyalty. Did he eventually relent and celebrate his brother's return? The story ends there.
This is a story about the father's great joy at the return of his son to the family. We are all members of the family of God. God loves his children equally and wants his family with him. To that end his son, Jesus, was willing to make the sacrifice for our sins. A question occasionally asked in this forum is: If God is so perfect then why aren't people perfect since he made them? Let's say you had a child and you had the power to snap your fingers and make it so that child automatically loved you and did exactly as you wanted. Would you do it? Would the love the child showed you really be love? Free will is a precious gift God has given us. Do we squander it? Do we grow resentful? Do we join the celebration? Do we make sacrifices for the greater good? Do we allow resentment to grow into bitterness and hate?
Imagine you were the parent of one of those innocent schoolchildren the gunman chose to kill by his free will. You know that you cannot bring your child back, but as a christian you have the knowledge and faith of resurrection in Jesus Christ. You know that your child is in paradise with the Lord and that you will see that child again. You take comfort in that although it hurts immeasurably. Now imagine that the gunman was also your child. We are all God's children. Does God love the gunman any less? No. Like the rich man with the prodigal son God is always willing to forgive if we choose to let him. Yet some people, like the rich man's other son, are unwilling to forgive. They deem themselves more special. Some even want to be their own god and live by their own rules causing great suffering to God's children. One of God's greatest gifts to us is our free will to choose. Yes, it does seem unfair that people should suffer at the hands of those who choose to hurt them and yes those who commit such acts may feel that God could never forgive them because it is only fair that he should not, but he will if they choose to turn to him with true repentance. God wants all his children to be saved at the end times. It's not about revenge. It's about love. Most people cannot fathom the depths of God's love. Justice used to be an eye for an eye and a tooth for a tooth, but that only leaves a lot of people eyeless and toothless. Jesus shows us a different way. Well, that's my opinion anyway.
I believe in God. I can't really point to one tangible reason why, I just do. The bible shows us who God is through Emmanual, his son Jesus. I heard a gospel song recently where the singer claimed to be satisfied with Jesus. Jesus said when you look at me you're looking at the father. If you want to know who God is look at Jesus. I want Jesus' goodness to rule my life. I don't think I could find any better.