If God is a supreme being, then He has the right to do whatever He pleases, and what is right/wrong is dependent on Him, not on you. If you think you are better than God, than obviously you are the one in rebellion and are putting yourself as god. It doesn't matter if you think God is just or not, because He is the one who can see things more clearly (perfectly) than you, and you are a creation of His. Doing what is right in your own eyes only leads to destruction.
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What shall we say then? There is no injustice with God, is there? May it never be!
For He says to Moses, "I WILL HAVE MERCY ON WHOM I HAVE MERCY, AND I WILL HAVE COMPASSION ON WHOM I HAVE COMPASSION."
So then it does not depend on the man who wills or the man who runs, but on God who has mercy.
For the Scripture says to Pharaoh, "FOR THIS VERY PURPOSE I RAISED YOU UP, TO DEMONSTRATE MY POWER IN YOU, AND THAT MY NAME MIGHT BE PROCLAIMED THROUGHOUT THE WHOLE EARTH."
So then He has mercy on whom He desires, and He hardens whom He desires.
You will say to me then, "Why does He still find fault? For who resists His will?"
On the contrary, who are you, O man, who answers back to God? The thing molded will not say to the molder, "Why did you make me like this," will it?
Or does not the potter have a right over the clay, to make from the same lump one vessel for honorable use and another for common use?
What if God, although willing to demonstrate His wrath and to make His power known, endured with much patience vessels of wrath prepared for destruction?
And He did so to make known the riches of His glory upon vessels of mercy, which He prepared beforehand for glory,
even us, whom He also called, not from among Jews only, but also from among Gentiles. "
Romans 9:
http://www.biblegateway.com/pa...=romans%209&version=49
Also, read
God's response to Job at end of the book, and reading all of Romans (not that long, all is online) will give you better background.