A series of pro-Palestinian protests targeting an Israeli cruise ship around Greece have irritated a conservative government walking a diplomatic tightrope with Middle Eastern powers during the Gaza war. At the crack of dawn on Thursday at the port of Piraeus outside Athens, dozens of riot police armed with truncheons, tear gas and shields sealed up a cruise terminal from hundreds of demonstrators. Their ire was directed at the "Crown Iris", a hulking Israeli tourist ship that has attracted protests at each of its stops in the country since last month. Tourism is a pillar of the Greek economy, but...