Because many Israelis are dual citizens of prosperous and peaceful countries of Europe and America/Canada, they would be tempted to just go back to those places instead of dying for a 'Cause' based on some ancient 'Claim' to a semi-arid land in perpetual warfare for thousands of years. But for Palestinians: Either live in 'tent cities' or as 'refugees' in the surrounding Arab states or die. Cornered tigers fight back hard!!
The same situation must have been felt by the Native Americans against the European colonizers and so they didn't much differentiate between the 'civilians' or women and children as they too fought desperately for their survival and a lot of time killed everyone they could.
In short, terrorism is the weapon of the weak! If the Gazans had the weaponry, the money, the numbers, then probably would have preferred to 'resists' in a different way. In the same way, George Washington didn't fight the colonizing Brits man to man a lot of time, as was the honorable norm those days, and used ambushes. As I said, one of my professors here in an American college literally said something like 'by today's standards, George Washington would be called a terrorist'.