The threat of a second Holocaust, undertaken against Israel by Iran using nuclear weapons, is a strong argument in favor of Israel being a shared land.

DETERRENCE

The presence in the Holy Land of a mixed multitude, especially Muslims, is a deterrent to Islamic nations using weapons of mass destruction there.

Concentrating a Jewish presence in a narrow, segregated land is its own danger to the survival of Judaism.  A different model of politics and social engineering in Israel would likely add measures of security not currently present.