To think that people actually think that God is dead, as opposed to that there never was a God in the first place, is a straw man argument. The concept of God is dead in the minds of many. That is what is meant by that statement. It’s not fair for Christians to make a movie about an atheist professor (played by a Christian actor) saying that God is dead in a way that is different from how the expression was intended. Instead, I would say that the Judeo-Christian concept of a deity who created the world, judges our behavior and cares whether we believe in him or not is dead. Of course, it isn’t really. If it were, there would be no more people who do believe in such a deity.