1. Why?

2. EU membership doesn't end Turkey's NATO membership. Why are Turkey's potential wars less worrying than instability affecting Bulgaria, Romania and Croatia?

The only reason I can see is the Kurdish question, but all this is contingent on the same human rights process all the other entrants had to go through. It's imperfect but it's certainly capable of either stalling Turkish membership or helping to solve the problem in some ways. Separatists are not a new issue for nations within the EU.

3) As opposed to a historically and culturally grey area between Western and Eastern Europe? Or between Sweden and Greece?

It's perfectly legitimate to be anti-expansion, but to suggest that Europe is not a cultural grey area in itself is a lie that needs resisting.