While it may have been offensive to the Turks and seen as a hedge to them, the ability to be able to invade your own country is a valuable ability. Specifically with air power and naval power. So why Syria may use the S-300 to block Israel airspace prevent take off. As they then invade the Galilee and Golan. The ground forces still have air support. Until the S-300's are dealt with.
Palestinians report IDF airstrikes on Islamic Jihad targets in southern Gaza Strip (Haaretz)