Even though I am a sede, it just seems crazy to me that a super conservative NO priest who is just hanging on to the NO out of a false sense of obedience is not really a priest. Since he is not a priest, would I just call him MR. Smith instead of FR. Smith? Even though I accept that Pius XII/possibly Cardinal Siri was the last visible pope, this just seems kind of crazy.
I think courtesy demands to call them with their respective titles they claim.
Also, what should a "sedevacantist" do inside a Novus Ordo church? Would he talk on his cell-phone since he doesn't believe that the Eucharist is present? Does he genuflect, or just walk out without making any external reverence?
If he is firm in his belief, then he wouldn't genuflect, etc. But by not doing so, he is only giving the other Novus Ordo Catholics a bad example to keep on following.