Italy is not unlike other smaller institutions which legislate one thing but do another.
It's not unique to Italy, but in this murder case there is:
1) the application of law
2) the protection of reputations
Those two things are definitely in conflict here. The only reasonable explanation for someone like Machiavelli to say what he says, in the face of the bad-facts (like Grinder's continual quoting of what Massei actually said, like RoseM's posting of the photo of the exposed balcony lit by a streetlamp, like Mach himself claiming lay-expertise in sleep-sleep deprivation issues where he does a clinical appraisal based on writings!, etc, etc.)
(Like Mach admitting that Knox/Sollecito were suspects from Nov 2 onwards, yet defends them being called to interrogation on Nov 5 and denied lawyers and the right to videotape/transcription of the whole interrogation....)
.... the only reasonable explanation is that Machiavelli is taking the side of protecting reputations.
That's not really as rare as one might think. Pick a country, pick an institution. They all do it. There are rules, then there are unspoken meta-rules. Machiavelli is better at these meta-rules, the unspoken rules that usurps the written law - things like, you never should insult a Public Minister or question their integrity.
If you do, its calunnia for you! Or defamation! Sheesh, they have a written law to use as a weapon to defend the unwritten ones!