As far as I know, there is no reason to believe they spoke Greek. Their alphabet was unrelated to the Greek, and Minoan culture may not have even been of Indo-European origin. Are they considered Greek for any reason other than that Greeks would later settle Crete?
Sorry, have to ask the question, who classes Minoans as Greeks? I've generally found the term Greek to be little used (aside from in the context of discussing Homer when people are too lazy to write Achaean) and certainly not in academic history until the Dorians came on the scene (well after the fall of the Minoan Civilization)..
Essentially I am asking in a long winded manner, who considers them Greek? (Citations might help)