well the persians were not mooslimb at the time, and as I recall they ultimately did sack athens and do considerable damage to the greeks.
A lot of freepers and conservatives, and apparently everyday Americans judging from the box office figures, approve of the movie because it is also supposed to be a pro-islamofascism-war themed film.
Very probably won't go out to a theater and see it, personally.
P.S. Not much a fan of ancient Greek "civilization," so that could have an effect on opinions about this movie--especially their glorification of the Greeks (Spartans), and acting as though they were macho-ly heterosexual.