You can criticize but maybe have documentation if you go around accusing people of stuff ...
If you are writing about real people online, especially when accusing Church people of heresy and subversive activities - make sure you have all your facts straight. Have backup, links, exact quotes, footnotes, and so on. In other words, have documentation, be able to identify your sources - and get it in writing. Especially if you name names or call people out as this or that. Religious people can be very litigious. Calumny and detraction, defamation and slander, are also sins. I may wrong, but there are canonical channels - especially for accusations of heresy and conspiracy. The case has to be heard, reviewed and adjudicated by the appropriate canonical authority. Good luck with that, though.
If you do get sued, you can maybe do what dioceses around the country do - just declare bankruptcy. Kidding.
That said, it seems to me the Catholic blogosphere is turning into a sewer.
What goes around comes around.
UPDATE: Fr. Geiger has posted on a different defamation case that has been circulating online, noting the "habitual refusal to accept personal accountability for the damaging information that has been released" on the part of bloggers:
The first point to be made is that the sources for recent the “reports,” are not responsible news outlets but bloggers, all of them, except one, are pseudonymous or anonymous. They have provided no evidence, that is, they have made purely hearsay allegations, or otherwise claimed to have “evidence” from which they have quoted excerpts without producing the document or its context. All the sources for these reports are clearly biased against the Commissioner and the Holy See and the bloggers in question are working in concert (Rorate Caeli and Correspondenza Romana, for example, regularly repeat and support each other’s reports).
Again, no reputable news outlet has taken responsibility for such “reports.” As far as I know—at least in the English-speaking world—no responsible news outlet has even repeated these stories emerging from the blogosphere. Please consider that when real journalists publish information from anonymous sources, the reporter takes personal responsibility with his real name, and the organization attempts to confirm the information by evidential reporting of independent sources. Nothing like this has ever been attempted by these bloggers. On the contrary, as already mentioned, there is an incestuous relationship between the various bloggers and their sources, and there has also been the habitual refusal to accept personal accountability for the damaging information that has been released. - Fr. Angelo
"Brothers and Sisters, this is the state of the Catholic Internet. It is a disgrace and a scandal to the world." - Fr. Angelo