Taking Jesus to Court
There's a reason Cascioli has a leg to stand on. Don Righi (and the church in general) preaches that Christ was a historical figure who actually existed. If this can be proven false, Don Righi will be found guilty of "Abuso di Credulita Popolare" - translated roughly as abuse of popular belief, or abuse of popular gullibility. Yes, in Italy there are laws that protect the innocent stupid from being exploited by conmen, swindlers and other scum of the earth. Essentially, the priest will be found guilty of willfully perpetrating a lie. And in Roman Catholic Country, where tithes and contributions to the church are taken very seriously, it boils down to the church being a very profitable pyramid scheme.
Of course, the judgement of a court of law is unlikely to affect the actual beliefs of the faithful (Kitzmiller vs Dover for example), and in Italy where the Catholic church is king, Cascioli will be lucky not to be ordered out of court. However, should he be able to convince a Judge to actually hear the case, this could shape up to be the trial of the century.
There is significant historical evidence that points to Jesus not existing - take Herod's slaughter of the innocents for example, which is cited as the reason Joseph hid his son's birth by at least one gospel. Historians at the time have recorded no such thing, and you'd think the slaughtering of thousands of innocent children would make some mark. Even some of the gospels fail to mention it, and you'd think that at least would be a big enough deal that the Apostles could all agree on it. One gospel even has Jesus being born at Joseph's home and not in a cave or stable on the run from the law (not a very exciting nativity). Additionally, comtemporary historians such as Pliny the Elder make no mention of a religious leader called Jesus. A number do however talk of John the Baptist, and there seems to be no real doubt that he existed. All historical records of Jesus, however, appear to either be second-hand retellings of the christian version of things, or outright insertions into texts at a later stage by pious frauds. No non-biblical texts of the time provide any information on the life of Jesus Christ that is not a blatant retelling of the Bible.
Of course, non-existence of evidence is not evidence of non-existence, so 2000 years after the fact it is unlikely that anyone could prove conclusively that he did not exist. On the other hand, proof that he did exist would be simple - find some record that is not likely to have been subjective or falsified. An entry in a roman census for example. But such evidence does not exist, or has yet to be discovered. To be honest, I don't see the case going anywhere other than a judgement for the defendant due to reasonable doubt. But it's certainly going to be an interesting ride.