I think this is kind of a double bind. The diplomat supposedly is not openly gay, and may just be somebody with homosexual inclinations (although a lot of those people are actually kind of asexual but now get forced into being homosexual) who acted on them at one time or another. But maybe he’s really not interested in defining his entire life as “gay,” and is not sexually active with anybody, but the gay lobby wants to “out” him and make him identify as gay.
On the other hand, it may be a challenge to the Pope, although I think that if the potential diplomat were more overtly gay, the Pope would be more accepting. After all, the Papal Nuncio (Ricca, an Italian) who got kicked out of the Dominican Republic for bringing his own boyfriend and frolicking around with him is now in good standing with the Vatican and taking on other tasks, thanks to Pope Francis.
I doubt that it was the Pope who opposed the French diplomat, but was somebody in the diplomatic corps, and this will probably be reversed after the Pope sends that person off to Siberia.
So, like I said in those threads congratulating Francis, there could be another reason for the “rejection”.