As we have become more advanced in our technology, and especially as the world sees every act an army performs, we become increasingly sensitive to who is a combatant and who isn't. Also, our weapons have become deadlier and deadlier, so if we aren't discriminating, alot more people die. (on an absolute scale, that is) Thus, it seems to me that our desire to discriminate is a modern luxury of sorts. Luxury in that it hasn't been available for most of human history, but also a necessity for our sense of justice.

In the ancient world, if the invading army was less discriminating (and how could they tell who had advocated surrender or resistance?) it would also be a natural effect that the populace was more unified, at least in each city. Following that chain of logic, it stands to reason that if an attacker today is less discriminating and highly destructive, the populace is more likely to band together where they otherwise might not.

Israel is pretty united against terrorists and the intifada, but these attacks are in most cases relatively low-impact. The Palestinians, on the other hand see highly indiscriminate attacks combined with a generally pretty high-impact. Regardless of individual houses destroyed, and who was or wasn't there, the massive destruction of infrastructure (the power plant and other basic services) in Gaza I deem to be 'indiscriminate,' since it affects everyone.

And if people standing outside a building makes them terrorists, then Gandhi was a terrorist. What about the line between huge 'response' missile attacks targeted at basic services and the random rockets going into Israel? How is one side dubbed 'terrorists' but the other completely legitimate actions... only because they're carried out by an officially recognized government?

One difference, at least theoretically, is that Israel, whatever actions it undertakes, has not sworn to destroy it enemies at all costs. But it's clear that not all Palestinians have either... although they did elect a lot of officials who have.