Who says that's why he created humanity? And if God's the creator, it's absurd to ask who gave him the right to do anything. God doesn't answer to another.
Then I can say I don't answer to another. Simple as that. Which means your god has no authority over me. If you can't site a reasons for why god would have authority your argument means nothing. Plus, you are obviously not familiar with all theological concepts concerning this god. According to some traditions, god and his wife, came from their parents, who came from their parents, who came from their parents, and so on and so forth. There are beings with a higher level of perfection and power. If one of them decides to see how this god is raising his children, see's the world like this and kicks his butt out of our realm then how much will you claiming he has authority matter? Not one bit. So no, he has no authority.
It's not God's power, but his authority that gives him the right. His power might provide some incentive for creatures to obey, but that's not what gives him the right to determine what's right and wrong. Besides, God doesn't "determine" what's right and wrong. God is the way he is, and God's personality, plans, intentions, and creative purposes determine what the rules are for us. It's not as if God has to think about what's moral.
Your right on the last sentance, god never thinks about what is moral. The bible makes that clear, he has no concept of morality what so ever.
Again, the issue has to do with the distinction between the wise creator and the ignorant creature. Being the creator gives God certain rights that do not apply to his creatures.
Wise creator? You must have a different definition of wise than the rest of us. Unless you think that child abuse, slavery, racism, mass genocide, and calling bats birds is 'wise'.
This is precisely what I'm getting at. Murder is a high-handed killing, arrogating to yourself a right that you don't actually possess to take the life of another. God has the right, but we don't. Thus there are times when God directly kills and also when God uses human proxies. And he also provides legal mechanisms that involve the killing of offenders (i.e., capital punishment).