Earlier quoted context omitted.
I don't think it's fair to put this on either the EU or Turkey alone. There were many factors prevent Turkish membership but the parent is right: religion played a huge role in the public opinion. I remember Merkel actually saying that Europe was founded on "Christian ideals" (nevermind the actual ideals having more to do with post-renaissance secularism than original Christian dogma) -- the same Merkel nationalists…
>the actual ideals having more to do with post-renaissance secularism // Could you go in to that a little, a few examples maybe of the main non-Christian ideals that underpin the founding of Europe.
https://en.wikipedia.org/wiki/Age_of_Enlightenment
the central doctrines [..] were individual liberty and religious tolerance in opposition to an absolute monarchy and the fixed dogmas of the Roman Catholic Church [..] along with increased questioning of religious orthodoxy.
https://en.wikipedia.org/wiki/Libert%C3%A9,_%C3%A9galit%C3%A...
The ideals of the French Revolution eventually became the underpinnings of both the US Constitution and the European and UN Declarations of Human Rights. The reason why they're called non-Christian is because they originated as a countermovement to religious doctrine.