We belong to God, yes, but we were created with free will as were the angels. Man would not be able to love if he were not able to not love. Man could not do good if he were unable to do evil.
God certainly can do with us as he will but he wont exert his will on us without our participation because he loves us. He is no authoritarian dictator.
I would be very when assuming people have not studied their faith or have not contemplated it deeply because it doesn't conform to your beliefs, that is arrogance and pride.
Including evil and darkness.
And everything else.