There are several useful arguments here.
1. Books send messages. SMeyer once stated that she "doesn't write messages in her books." Even if she doesn't do so intentionally, that doesn't mean that they aren't sent. There are many bad messages that the book sends: 'racism is okay,' 'abuse is okay,' 'women don't have the natural right over their bodies,' 'suicide is romantic,' and more. It doesn't matter if the events happening in the book aren't real, or the characters in it aren't real: the messages are REAL.
2. People analyze books. It's something they've been doing since the dawn of time. Look anywhere on the internet and you will find this to be true. Why do people do this? Well, if you dig deeper into a book, it helps you to figure out what it is about it that you like, or dislike, so much. If you provide your analysis for other people to read, it allows them to see the book from a different angle, and it too gets them thinking. These are all good things. There is absolutely no reason in the world why Twilight should be exempted from the common practice of analyzing books. None.
3. Clearly, there are many Twilight fans who disagree with the fact that they're "jus fiksun," through their screaming out names, buying merchandise, covering their boyfriends with glitter (go read My Life is Twilight to see what I mean).
4.. We have the right to our own opinion. Freedom of speech? Freedom of thought? Besides, there's as many--if not, more--Twilight fan sites all over the internet. Why would fans be allowed to voice their opinions on a book, but we don't? By doing this, we are spreading the truth about Twilight, in all its bad messages.