Apology in this case means admission of guilt. After receiving an Israeli apology, Turkey will have no other choice but to request murder charges be personally filed against persons acting in the incident. An incident in which people die cannot be washed using simple diplomatic formulas. Israel did nothing wrong here, and has nothing to apologize for. Admitting wrongdoings when one is innocent is a very slippery road. The Jewish people suffered enough from blood libels, and does not need creating a new one by his own hands.
from the article: Deputy FM: Israel won't apologize for Gaza flotilla raid