This comment in that thread hit the nail on the head. Americans just don't want foreign courts to prosecute their citizens.

I think there is a lot of evidence that points to her guilt. But I think a lot of people are uncomfortable with the idea that an attractive young american student could be inovlved in a horrible crime like this. If it's true, it makes us all look bad. Easier to blame the Italian courts of misconduct than to admit the strong possibility that Knox was involved in this murder.

I think people should ask themselves, is their opinion based on the reported facts, or is it based on the idea that they don't like a foreign court deciding the fate of an american? If the exact same event had taken place in Boston, would you feel the same way?
Sorry if you commit murder or any other heinous crime, your ass isn't above the law just because your country is a superpower.