First of all I didn't comment on the photo at all. To directly answer your question, why would any intrusion be acceptable. If John Kercher did a book signing event for his book and somebody put up a picture of Amanda with a caption the wrongly accused friend of Meredith, would that be okay?
I know this is almost impossible for any PGP, but just imagine that Raf is completely innocent. At the time of this book signing he was not guilty under Italian law. Having accomplished that state of mind, can you see that Raf would be seen as a victim of the system and that Meredith death had nothing to do with him accept being used to persecute him.
If he is found innocent by this next court and it becomes completely clear he had nothing to do with the murder would it be okay to keep showing Meredith's picture anywhere he goes? If one of the british girls writes a book about their own life should people be allowed to project a picture of Meredith against her wishes?
The PGP seem to think they own this entire tragedy. They want the house turned into a museum at the landlord's expense. They keep saying Meredith shouldn't be forgotten, ignoring that she hasn't been forgotten precisely because of the kids fighting this conviction. Had they copped a plea, Meredith would have long been forgotten.