Secondly, their sin was passed down to every person ever born
How nice of your god to curse the entire human race because his original "creations" were flawed.
How can a 'perfect' being create something imperfect? Stew on that for a while.
Before you throw in that tired "free will" argument, free will showed just how imperfect Adam and Eve were (humoring the possibility that they existed in the first place).