I think his point (and it is a ridiculous point) is that foreigners who buy in Turkey and sell on prevent a 'new' sale happening to a 'new' foreigner, thus losing the chance of making 2 sales to foreigners. This is in his opinion the reason for the downturn in sales to foreigners, nothing to do with credit crunches or economic downturns at all. Taken to a conclusion his view is that foreigners who buy a property in Turkey should keep it forever.
His position is financed by the estate agents he represents and I feel absolutely sure his views do not represent the views of his member agents. Posters and leaflets at airports? Let's hope that people arriving at Dalaman to meet estate agents don't see any of his posters or leaflets, or warnings about renting properties out might just cost his members some extremely valuable sales.