The biggest problem...
People always use films like "Exodus: Gods and Kings" to start religious debates. Atheists use it to attack people with a belief in a higher power (one review which made its way onto the film main page is titled "Excellent to expose the stupidity of biblical literalists" and uses the opportunity to berate everything supporting Biblical history); religious people use it to condemn people with their "You're gonna burn in hell!" tactics an open rejection of any form of reason.
In short, not many people on these message boards seem to operate in love. Christians should, because they are commanded to by Jesus. Atheists should too, because (in my experience) they all seem to feel 'superior' to Christians because they believe they have the answers to all of life's origins, and if that were the case then they should have a deeper sense of love towards their fellow human.
At the end of the day, and I am happy to be proved wrong about this, people on here are not professional archaeologists, not experts in ancient cultures, not experts in Biblical theology of the ancient languages in which the Bible was written, and most aren't even experts on film. Now, that shouldn't stop the discussion from taking place, but it's something that seems to be forgotten and results in so much anger and hatred being thrown around.
If we're the result of 3.5 billion years of evolution, why don't people act like it? If we're the result of a supreme Creator, made in His image, then why don't we act like it? I feel ashamed to be the same species as such people.
That aside, the problem with "Exodus: Gods and Kings" is that it deviates from the the Biblical text.
Before you start thinking, "But the Bible isn't real anyway!" you need to think of it like this: have you ever read a book and then watched the film and been annoyed that the film was different?
I was disappointed with "Lord of the Rings" because they missed out Tom Bombadil, as well as other things, and also added extra things. This is the same problem with "Exodus". As with most book-to-film adaptations, it doesn't do the source text justice.
The only times I've enjoyed both book and film are when I've seen the film first. I loved "Starship Troopers", and then I found the book incredibly different (including one character having changed gender as a result of the adaptation!) but it was still great. The same with "The Neverending Story": fantastic film from my childhood, and a great read later on (I was an adult when I read it).
So the debate isn't about Biblical historical facts or religious propaganda, it's about whether the film does any justice to the source material. Sure, some things do need to change in order for the film not to be dull, but that should be the exception, not the rule.
If a filmmaker wants to produce a story about a bunch of slaves being freed as they followed their religious leaders, but doesn't want to stick to a certain source material, why not just make up their own story? (Of course, by using the Bible as the source material, it ensures the film is a box-office hit: for Christians because they think it'll support their beliefs; for atheists to criticise it for how "stupid" it is.)
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When it comes to being a role model, "good enough" usually isn't.