You have got to be joking. You seriously think that in some future Islamic-majority America that Muslim government officials who would otherwise want to quash Christianity will be shaking in their boots, their plans thwarted because of the 1st Amendment, much less some dumbass ruling on courthouse decor? I can imagine it now... "Darn it, Achmed -- we would have gotten away with it, too, it weren't for those 11th Circuit infidels and their meddling Constitutional interpretation!"
It doesn't have to be a future Islamic majority America. Think smaller, specifically Dearborn MI (if they could take over Wayne county), or if Muslims decided to take the route of the Free State Project and concentrate in a small state or even a county. The chief judge of the county or state, using Moore's reasoning, could order that county and/or state courts to display Koranic banners and other symbols of Islam to the exclusion of all other religions and the feds could have no say.
The Constitution is not worth defending only while people like you or me are in the majority. If you don't understand that, I'm hoping most people here do.