That Bashar al Assad is the prime source of current instability in the Levant, is fact. That Assad's regime has perpetrated a civil war against the Syrian people that has killed in excess of 200,000, is fact. That Assad's regime has caused the uprooting of some three million Syrians from their homes, is fact. That Assad and his forces are responsible for gassing to death at least 421 Syrian children and another 1,000 adults in one event, is fact. That the hereditary leader and his army has barrel-bombed civilians across Syria, is fact. And that Assad's atrocities against the Syrian people has directly contributed to the swelled ranks of the terrorists ISIL, is fact.
Thus, to begin to end the terror, reign and widening influence of the ISIL, the source of the group's main recruiting tool - Bashar al Assad, must be capped. I opine once again here, that actions against the ISIL while Assad sits in Damascus, would amount to mere cosmetic damage. The ISIL will be difficult to defeated until the source in Damascus - Bashar al Assad, leaves the throne of Syria. He is the single most source of governance hatred.
So with respect to Turkey's unstated desire to pave a road to change to Damascus, Ankara infers an understanding of the implications of a continuing Assad reign of terror. And in spite of what other agenda Turkey might want to fulfill with the demise of the Assad regime, Turkey rings true in determining that Assad's status has been reduced to one of "persona non grata".
The youths of the Levant, Europe and other western countries are being exploited by the ISL based in part by fallible religious dogma and mainly by the underscoring of the atrocities of the Assad regime. So as the ISIL is defeated town to town and desert to desert, mutations of alternatives to the likes of Bashar al Assad will continue to pop up until the Assad-style leaders of the world are no more.