More importantly, the dates in his link are about 10,000 years too young for the claim he's making. How is a claim by archeologists of human presence on Easter Island form perhaps as early as 900BC evidence of an advanced civilisation there 12,000 years ago that was part of the same civilisation that built Gobleki Tepe?

His link says nothing about advanced civilisation building stone structures 12,000 years ago. In fact it explicitly claims that the dates they are providing are explained by a human presence that pre-dates the building of the Maoi by centuries. Does he actually read his own links, or is he, as I suspect, just Googling for anything that he thinks he can throw out, just because a precursory glance at it seems to be vaguely related somehow to his claims, even though it really isn't?
I can guess at his response - just because no-one has found evidence of civilization on Easter Island from 12,000BP, doesn't mean the evidence doesn't exist and won't be found in the future. So far the only evidence he's presented that both Gobleki Tepe and Easter Island were part of the same 12,000 year old advanced civilisation is that some stone carvings from both look the same, even though the evidence is that they are separated by thousands of years and literally the only thing about them that fits his hypothesis is that they look a bit the same.
Which is, to say the least, not a very scientific approach. If in doubt, just pretend evidence exists but simply hasn't been found yet. He's pulling that tactic out a lot in this thread. Anyone can make wild claims and then make excuses for the evidence not existing and how someone at some point will find the necessary evidence.