Killing each other is not what God wanted, even when we don't know much about Him, or even recognize the same god as others believe in. Any killing has to do with getting rid of people who are so extremely evil that they are wrecking society for everyone. But we have governments to do this.
As for God creating mankind... We don't know much of the thinking of God. If God, for His own purposes, created mankind, say, to rule the universe, or to colonize other worlds, how would we know except if He made that knowledge available to us?
If people had remained in perfection (Garden of Eden) so that they never died, populating other planets is exactly the thing that God might have wanted. After all, when populations on Earth are so great that there is standing room only - and such is what would have happened if there were no sin and death, and especially if everything had remained as healthy as it was in the beginning, people would populate faster than rabbits - where would they go just to live?
God hasn't revealed the plan that He had for us at the beginning. Why not? Because we sinned, and death entered. The whole scene changed. Population no longer has to do with going to the stars. Rather, it has to do with finding a way out of death. And not out of death for those who are still alive, but out of death for all who have died, as well.
Take a look at Ancient Israel in Exodus in the Bible. Israel was going to the Promised Land. When they got to the borders, they rebelled, and didn't enter in like God wanted them to. So, God told them that they would have to spend some time (40 years) wandering around in the wilderness. But then they tried to go into the Promised Land anyway. And a bunch of them died for it.
Now, we are trying to go into space, to populate the moon and Mars. This might have been the plan in the beginning, but mankind changed the plan by sinning. It won't work... populating Mars. A bunch of people died trying for the Promised Land in the Exodus, and they will die trying for Mars.
The point? If there are aliens out there, they are only there to maintain the planets until mankind would get there. But we don't know that they are even there.
The thing we should be doing is working with God in His method for us to live forever, and to even bring back life to all those who have died. What is this method? Jesus salvation!
You're basing this from a book that was compiled less than 1500 years ago. And the final product was decided by people like you and me who actually had power at that time. This should clearly be something to be considered, right?
And again, I come to the scale I'm talking about. The universe. Believed to have started billions of years ago. If you have the power to create something of that scale, would you seriously focus on what a certain specie is doing, who they're worshipping, what they were thinking etc? Seems quite petty for someone who's that powerful, right?
And I don't think you're serious about aliens taking care of other planets for until such a time that humans can go there lol.
But, try thinking a little more. Here's some more thoughts.
1. The book compilation had other writings considered. These other writings don't change the book regarding the way we are talking. In addition, the compilation was done to clarify what was the truth. It was done by comparing the basics of the Hebrew canon with the Books that would go into the New Testament, and with the Apocrypha. Books that added things that weren't supported by the canon were left out. Books that had items that weren't verified by other N.T. books were left out of the N.T. The process was meticulously done.
2. The universe is believed to have started about 6,000 years ago by many. The fact that others believe it to have started billions of years ago, shows that they have a religious belief. Pick your religion.
3. If I have the power to create something on the scale of the universe, how in the world can something as tiny as you second guess me or what I have in mind? My thoughts would be way beyond yours... to say nothing about the fact that you can't even read the minds of your fellow humans.
4. God says in the writings he authorized, that His focus in creation was making and supporting mankind.
5. The Bible talks about 13 classes of angels. Some of them take care of the forces in the whole of outer space - the universe. --- Look in the Revelation for the part about the Dragon's tail sweeping a third of the stars out of the sky. The standard understanding is that these stars were angels. Satan, the Dragon, the Devil, whose name means Destroyer (in Revelation), thought that taking a third of the supporting angels out of the universe, would certainly destroy the universe. What He found out is that the whole universe is upheld by God... through the angels, or not through them.
6. The idea of humans going to space is my idea. But consider the context of it. If people had remained perfect, and never died, it wouldn't really take long for standing room only to be achieved on Earth... and faster than ever considering how healthy the earth was back then.
But thanks for giving me the chance to explain some of these things.