"Right and wrong are just ideas. What matters is what you do."
God, speaking to Bender on the animated series, Futurama.
The short? They're both wrong. Hamas was wrong to take control of Gaza and to exploit the Palestinian people, and Israel was wrong to let it happen. Israel has been a racist state since its inception (black Jews were marginalized by white Jews and kept from holding office or Knesset seats), and refuses to get along with their mainly-Arab neighbors.
Not that the US will do anything to stop Israel - they're one of our biggest arms customers. Whatever military capability they have, the US sold to them.
Hamas is wrong to fire rockets into Israel from Gaza (from primarily civilian locations) and Lebanon. Israel's response is ridiculously heavy-handed and violates the Geneva Protocols in several ways. Over 1/3 of the casualties in Gaza have been civilians (if not more).
Its the bloodiest example of "Two wrongs don't make a 'right.'"
PS to the other answerers, Israel is NOT a democracy. They are the only Jewish theocracy (pretending to be a Parliamentary Democracy) in the world, and the first such state in hundreds, if not thousands of years. They do NOT grant equal rights for all. If they did, no one would really have a problem with them. Read through the Israeli Constitution some time.