Re: Why the 1970's?
Seriously, Super Jim brought up some really fascinating ideas and all everyone could muster up was "I don't think the movie is going to be in Vietnam..."
Did you guys even read all his other points?
I don't think they're going to have any scenes actually in Vietnam (and that might actually be too much of a side story), but the idea of Nixon and the conspiracy theories sound like a perfect storyline. Mystique, the ultimate spy, is perfect for meddling with this kind of subterfuge.