Israel asked Turkey to prevent the ships from sailing, like you think what the PM should have done. But in a democratic country, a PM should have no right to prevent peace activists from taking aid to another country, just like Israel should have no right to storm their ships and murder them on international waters. There were ships from Ireland, Greece, etc. too in the flotilla. So in your opinion, their governments should all have prevented those ships? You mihgt not agree with the world view of those people in the flotilla; I am not sure if I do, either, but saying that Erdogan should have prevented it is anti-democratic, i.e. something Israel is readily used to doing, and a democratic country like Turkey should NOT do such anti-democratic acts!
Police disperse hundreds in brawl in Kafr Manda, northern Israel (Haaretz)