Why don't we use the most recent massacre carried out in Gaza as an example? During the 2008 cease-fire between Hamas and Israel, it was implied that Hamas would stop firing rockets and mortars into Israel if Israel lifted its blockade enough to allow humanitarian supplies into the area. As Israeli data shows (see p. 6
here,) Hamas more or less honored the agreement by essentially bringing rocket and mortar fire to a standstill. Israel did almost nothing to lift the blockade, and the people of Gaza continued to suffer. Rocket attacks increased sharply once more as a consequence of Israel's inaction, and Israel responded by slaughtering Gazans.
Let's compare the number of casualties caused by Hamas' rocket attacks with the effects of Israel's massacre:
- People killed by Hamas' rocket attacks, 2001 - Jan 2009: 28 (source)
- People killed by Israel during the Gaza conflict, Dec 27 2008 - Jan 18 2009: 1,417 (source)
That's 30 people killed over an 8-year period versus 1,500 killed in a few weeks. That isn't "self-defense" by any stretch of the word.
I'm afraid most of the civilized world has evolved beyond "might makes right" notions of entitlement.