Jerome,
For those who are not students of culture, let me add this introduction. It's a fair generalization, at least in the Abrahamic religions, that those in any particular system of faith, consider they're on the right path to heaven, while others, although are valued as human beings, made by God, still are not equal before heaven. So for each religion, nonbelievers are less sanctified and holy in some measure. Furthermore, a lot of history is related to wars of religious conquest, exploitation and xenophobia so each culture has its sore memories of persecution and interference.
The huge sign in your picture does, on the surface, appear to reflect a nasty attitude to non-Muslims! However, that's not quite right. Of course it
is a bit of an insult, but it's not meant quite as such. Yes, we are considered on a different level. The sign, however, is actually a reflection of a generous compromise made by Muslims in allowing "heathen" non-believers into their houses of worship. It's pretty progressive that they would permit
any outsiders, given the animus experienced over the centuries and the current tension between Muslims and the West. Not all religions are that open!
I know that many Jews do not like non-Jewish visitors and especially with cameras in a house of worship and especially during prayers. From bitter experience, with caricatures of foreign-looking jewish stereotypes praying in a manner strange to Christians, with prayer shawls,
tallit, or strapped on leather phylacteries,
teffillin, to be ogled at while the congregation is in devotion, trying to be at one with their creator. This is a private experience, almost like congress of man and wife.
So I can well imagine how Muslims might feel "objectified" when hardly well-informed tourists pass through, as if visiting some circus tent showing the snake with three heads. OTOH, the vast Notre Dame Cathedral has no such defensiveness having tourists pass through. The Church is much more self-confident! The form of prayer? It's "normality" for most of the visitors and the Church would love folk to be moved and converted, as it's always looking to spread the word of salvation. Moreover, the place is sometimes rather empty, even during prayer, so added souls makes it more pleasant! The massivity of that Cathedral, the sheer beauty of the windows and the eminence of the architecture makes even a busload of tourists hardly noticeable.
When I visited the mosques in Turkey, visitors took off their shoes and were allowed inside and permitted to take photographs but not allowed in during prayers. Local folk seem to pack the places and they don't need, at this time, to press us into the congregation to make a quorum, LOL!
Asher