PKK helped YPG (Kurdish in Syria). YPG is an affiliate of PKK (another Kurdish grp). They both helped Peshmerga Kurds in Iraq rescuing Yezidis and fighting I.S. (ISIS). A fact that was hardly publicized.
It really depends on who is "officially" considered a terrorist. PKK and YPG are not terrorists, and certainly PKK, Before I.S. suddenly appeared on the scene, was actively attempting to make peace with Turkey after being persecuted, as a Kurdish group, by Turkey for many years.
Just what have the Turks done since 911 to justify them remaining in NATO?
They support Ham@ss and never let NATO use their air bases in Turkey. Their leader ERDO the Turdo is a radical Muzzie.