1) The movie doesn't look like the grand spectacle you proclaim it as. I think if the trailers showed more nephilim and demons fighting or warlocks using magic or what have you, that the interest in this would be much higher from the non religious side of this.
Instead this looks like nothing more than an attempt to put to life the Noah myth. The color pallette, in spite of being heavily filtered, looks drab. Human conflict, especially within the family unit, seems to be the center of the narrative. Even the special effects with the animals and the flood don't look particularly inspiring. Nothing about this looks fantastical.
Now, maybe the trailers don't properly represent the movie, perhaps because the studio is trying to hide anything that might offend either side. But that is what advertising is supposed to do; get me interested.
2) Whether it turns out to be a bible movie or not, the perception right now, not the least of which because of the above point, is that it is. And regardless of whether it actually is or not, due to that perception, the success of this movie legitimizes the notion that bible movies are okay.
We live in a time where there is, and I hate to use overused language like this, a war between the ideological extremes of religion and anti-religion because of the massive influence that they (atm religion) hold over so many other aspects of our lives (at least here in the US).
The people who absolutely want to remove the influence that religion has are unwilling to give even an inch to the notion that biblical stories are even worth considering. So long as this film gives even the hint that it might not treat the tale it is based on as fiction, then I think there will be people who decline to give it a chance.
I am not saying I agree with the stance necessarily (my lack of interest has much more to do with #1), but I do understand it, and I think its perfectly reasonable and fair of them to treat it as such. And no, I don't think those people owe Aronofsky the benefit of the doubt just because he made some other intriguing movies. It isn't incumbent on the viewers to determine the directors beliefs and intent before judging the movie (although they are welcome to do that if they wish). The movie should stand on its own merits, and if it looks and feels like a bible movie, then they have every right to treat it like one.