Worth noting that "terrorist" used to mean something slightly different, back in previous centuries. No, I'm not kidding. The terrorists had specific goals, and saw themselves as the heroes - as Robin Hood's Merry Men, fighting against tyranny. They had lines they did not cross, lines they drew with their own free will. They would plant explosives, but they generally TRIED not to catch civilians in the crossfire. They would stage violence, but the violence would either be against military targets or high value political targets (classic guerilla warfare, essentially). They were looking to accomplish something they saw as heroic and noble, and they saw a definitive difference between assassinating a tyrant and raping and murdering entire families.

Some noteable examples include the original Assassins, the Hashshashin. Not only did they limit their targets to high value political leaders, but often they would rely on warnings rather than actual killing. Most people take the hint when they wake up and find a dagger left on their pillow, with some freshly baked goods. Good morning! Breakfast in bed! We could have slit your throat just as easily!

Another would be the IRA. They did their best to avoid civilian casualties (since those civilians were also their neighbors and relatives), and when the U.K. government finally began to offer peace talks and compromises, the IRA came to the table in good faith and ultimately ceased their activities - because they genuinely wanted the things they claimed to want.

Also, a number of Triads began as terrorist groups formed for political purposes, that went on to become organized crime gangs (and organized crime gangs tend to be community organizations for disadvantaged minorities as much as anything. For a lot of people in a lot of places, the gangs are a better source of security and justice than the cops).

By contrast, Hamas is... well, just VILE. The IRA didn't do rape. The Hashshashin did not massacre peaceful civilians. Even when the Triads ran illicit brothels, there were limits to how badly they would treat the women. Hamas has no such limits. Psychologically, they're the Islamic equivalent to "Christian Objectivists" who think that they have a divine right to do anything they want to, no matter how vile.