I've recently watched that movie again. I just wonder is this a movie about history? Or just a movie with fake heroes (like superman). If it's fake, why they use real names of Persia and it's Kings? If it's historical, why they would put so much untrue information to audience's mind about Iran. As it's said in the most authentic resources, the kings of Achaemenid Persia, especially the founder Cyrus the Great, strongly declined to adopt slavery.
And the domination of Achaemenid, has never been forced to any people or nation (according to the first human rights statement in history, written by the great Cyrus). We can talk about history in days, and we respect if Hollywood wants to make historical movies (as it has made great ones before) but without doubt the world is extremely watching you, and giving untrue informations will lower your credibilty every day.