1- I have not seen The 300.
2- To my understanding, any “great” empire, including the loveable Persian one, became an empire because cities and territories were conquered. I can not imagine conquering a place, without killing people who, “mysteriously”, think they own the land. Thus, I “admire” all great Iranian kings for their sharp swords. For the exact same reason, I “admire” G. W. Bush for his sophisticated aircraft carriers.
3- Novels, movies, celebrities, TV shows and other similar stuff are produced for entertainment. It is bad to portray a nasty picture of others in order to enjoy yourself, and make money, but it is not a crime. At most, you can sue them or do the same to them, as if there is no Iranian movie ridiculing Americans and others.
4- Using Google Bombs, protests, angry blog posts, and mass emails for protesting against a movie is an overreaction, to my understanding.
5- Don’t watch stuff you don’t like to see.
6- As I have not done a DNA check, I am not sure if the Iranian “monsters” in 300 are in fact my ancestors.