I don't feel the founding of Israel was illegitimate. The facts are pretty clear if you go back and look - of course it was illegitimate. And the creation of Jordan, Syria and Iraq were just as illegitimate. No one polled the inhabitants and asked them what they wanted. The eviction of Jews from their ancestral lands in Iraq, Syira and Egypt was also an immense cultural crime. So was the eviction of Christians from those lands.
But none of that matters now, anymore than Greek claims on Istanbul matter. Israel has as much right to defend itself and its borders as any other nation. And it is perfectly clear that Hamas poses a real threat and are nasty vicious people to boot. No dispute on that point.
What contention am I running from? I suppose "legitimacy" was a loaded word and the wrong word. It would be better to say that VDH frames Israel's importance to the US in terms of its cultural, political and economic superiority to its neighbors. This is the framework for a foreign policy based on values rather than national interest. ..
Ivan has a point. Furthermore, as long as U.S. support for Israel has primarily this basis, it becomes an axis of attack upon the U.S.-Israel relationship.
The best response is that the U.S. has a very definite geostrategic interest in Israel's existence. That is, for the past hundred years the U.S. has had a policy - actual, if not declared - of "No more empires", because imperialism breeds war. (Empires, because of internal strains between nationalities, seek security via external aggression.)
For thousands of years, the natural state of affairs has been that the Levant serves as a battleground between Asian- and Egyptian-based empires. When one of these conquers the other, the new empire then reaches out to conquer Europe or India.
Except when Israel is in existence as an independent state. Then the formation of such a world-conquering empire becomes quite impossible. That was true in ancient times; it is also true today. Egypt tried to form an empire under Nasser; Iran is trying to form an empire under its mullahs; in both cases Israel makes that impossible.
The world is relieved of the threat of a world-conquering empire, but that means Israel has become the mote in the eye of would-be imperialists. That is the key reason for the U.S. to support it - even if Israel wasn't a liberal democracy but every bit as bad as Israel's enemies say!