I concur that a joint “service” COULD be problematical..
but I have attended several which were not any problem at all.
It all depends on how they are conducted, what is said of course.
There is SO much overlap (for obvious reasons) between Roman Catholicism, Protestantism, and Judaism.... especially in that much of the scriptures are shared..... that it is not really very difficult to conduct a shared service which does not undermine Catholic faith.
I have to assume that the local Bishop and priests down there did a competent job of conducting or preparing this event or service in the Cathedral. If that’s wrong, then I would have to stand corrected, but just holding a shared service or event in a Cathedral would certainly not be grounds for somebody to protest or disrupt it, presuming there were no preachings against the Catholic faith, etc.
I gathered from the article (and this could be a misunderstanding) that the protests were against the mere holding of a shared service or event, and not against any particular violation of faith or creed in the course.
Again, there could possibly have been something wrong happen, I just didn’t pick up on that
This “Spirit of Assisi” thinking was condemned by past popes. You would never have had a pre-Vatican II pope/priest sharing services with non-Catholics. Period.
Up is down and down is up.