there are lots of reasons we don't like iran. the first is, they want nukes which is compounded by reason two, they "hate" israel. now. the reason they want nukes is because israel "hates" them and israel has nukes (and has recently attacked syria, not to mention homg lebanon).
third, they're scary persians. have you seen 300? have any idea how we feel about iran? they threaten us because they were one of the original humungo-empires. now, they have this new factor of islam to unify them with other large groups.
four. did i mention islam? yeah. scary muslims. it's easy to pin the evil badge on anyone we don't understand.
five. human rights. this is legitimate. they really do have some stuff they need to work on. we do too, but we don't like to bring attention to that.
six. they have oil. i'm sure. if not, our president probably thinks they do. we want it and we don't want to pay for it.