Have you ever instinctively disliked someone without any justification and then later learned something terrible about that person that made you feel justified for disliking them? That is how Injustice makes me feel about Superman.
Turns out Lex Luthor was right all along, Superman did turn on the human race and become a tyrant. Injustice is outside of regular DC comics continuity and is thus an "imaginary story", but all the other Superman stories are imaginary too, so I choose to buy the self-righteous hypocritical Superman over the perfect boy scout Superman.