There are just so many wrongs with your point of view mate.

First, what you are implying is that if sovereign nations don't want terrorists attack them, they must negotiate with them. This perspective suggests that the US should have made official contact with el qaida, or ISIS so that they stopped attacking their country. This is complete bollocks, you never negotiate with organizations that are recognized as terrorist.

Second, just like there are Kurds in southeastern Turkey, there are Turks there as well. Turkish people, language and culture have been present in that region for hundreds of years, and Kurdish nationalism and separatism completely ignore this fact. They do not have the right to found their country in Turkish territory.

Third, the matter in Syria is not exactly the same with Kurdish separarism in Turkey, or Irish separatism in 1920s UK. YPG in Syria is an illegal organization as it violates a sovereign nation's territory, sells its natural resources to overseas nations like the US, then with that money buy heavy weaponry to arm their millitants. It just happens that their millitants use mortars and similar explosives on civilian structures in Turkey, in support of PKK. It is true that they want to found their own state, however every action they have taken so far has caused obvious security threats to the countries surrounding them. Turkey, Syria, Iraq have every right to defend themselves and act against such threats.

Kurdish nationalist just have to find a peaceful solution to their problem. Otherwise they just become terrorists.