Secular Arabic culture are you describe it is actually quite close to European culture. In what way is moderate Islam fundamentally incompatible with moderate Christianity?
Well the track record of the treatment of Christians living in Islamic countries around the world certainly isn't great. Unless you can point to a majority Islamic country with a successful and thriving Christian population?
However I'm not so much concerned with Islamic versus Christian values. Much more with the compatability of any form of Islam with a
liberal values such as: equality of religion, equality of opportunities for men and women, equality for gay/lesbian/trans etc.
It is for these reasons I don't believe giving Turkish citizens unlimited access to Europe is a sensible idea.