Hamas broke in large part because atrocities that they commit (including, perhaps most importantly, against their own people) are not overwhelmingly condemned, with the concomitant lack of support and active opposition that this entails. So we should vociferously condemn them and view those who don't as contributing to the problem. This is a critical step on the path away from atrocities and towards a humane resolution of legitimate grievances.

The reason Hamas is a Hamas-scale problem and not an IRA-scale problem is in large part that they are tolerated. (There are other reasons too, of course, but this is a big one.)

If Northern Ireland had been made independent, yes, that would also have solved the IRA problem (but likely would have caused other problems, and why shouldn't a local "Irish Monarchist Army" use IRA-like tactics try to switch things back?). But going, "Well, of course you have bombings and terrorism when you have British rule of territory that isn't Britain" would have made the problem far worse.

This is not the only reason why there is a problem in the Middle East. We need a multi-pronged strategy to try to improve the situation, including stern criticism of Israel (backed up by action if they don't heed the criticism). But given the difficulty, we can at least not make it worse by sparing Hamas from criticism or diluting it by using their specific atrocities as an excuse to talk about Nat Turner.