That's the difference mate - Israel defends itself, its agenda calls for a safe home for all the citizens of Israel, regardless of race, color or religion.
Have you read the Hamas charter lately? It stated they wish to destroy Israel and kill all the Jews.
Last I checked - An organization resupplying with weapons to purposely destroy another country and kill all of its inhabitants isn't exactly the best example of "self defence". For self-defence you have to be the defender - Hamas is most certainly on the offence.
Edit: To clueless "Link" - You do realize that Israel is the world's 3rd biggest EXPORTER of weapons, right? Among their clients are the U.S.(Mainly purchasing Israel's advanced UAVs and military technology), India, Georgia and plenty more. China were about to become one of the customers, but since the U.S. forbid Israel to sell weapons to China, the deal broke through. Israel even beats Russia's massive arms industry in volume of sales. Trust me - Israel would handle without USA's support as well. Not with ease, but would surely handle.