You don't think some of the offense is just possibly being over-hyped a little? Sure, people can be as offended as they want, but please don't be offended over other people's lack of offense - that's just offensive! ;)
If Sophies mom told her to tell her friend that her moms were filthy gays or anything remotely similar then sure, but she doesn't. In fact, the message recognizes other people have their own idea about what is right and wrong and at the end doesn't involve her being judgmental at all, just for her message to be about paradise and animals etc...
It's only in the context of "not getting into paradise" that being gay is portrayed as dangerous. So people are offended that they won't be invited to the imaginary land that they don't believe in anyway? I mean, I am also not invited to paradise - should I be equally offended? Should I call the newspaper?
Of course it promotes the idea that homosexuality is not bible-approved and that is the real issue - but it's not news, not shocking and to most conservative Christians, it would be offensive to think otherwise.