GREECE, May 8 (Reuters Breakingviews) - At one point in Homer’s Odyssey, the hero has to steer his ship between twin dangers: Scylla, a multi-headed monster, and the whirlpool of Charybdis. Leaders of the Group of Seven rich countries meeting this month in Hiroshima may feel they are in a similar situation when it comes to China. They don’t want Beijing to invade Taiwan; but they also want to avoid war with the People’s Republic. The best chance of steering between these twin evils is for the G7 to agree on a strong deterrence strategy. If leaders speak with one...