It was left up to the Israeli government in 1948 in regards to the "right of return" of the Palestinians into Israel, and that's why there's 1 & 1/2 million of them there now. Those that fought against Israel or supported the Arab countries that attacked, by and large were not allowed to return. Meanwhile, 5/6 of the partitioned land of Palestine went to Jordan as the Palestinian country, and most that now live there are indeed Palestinian. Over and over again the Palestinian leaders had a chance to go for peace, but they never did, and actions and often inactions have implications.
So, under attack by either Hamas and/or el-Fatah, including suicide bombers, what do you suggest should be Israel's response?
If I had verifiable Jewish ancestry, I would be allowed to be a citizen of Israel.
My friends of Palestinian ancestry are not made Israeli citizens by virtue of their bloodline, even though it is derived from the same land, and has left there far more recently.
It is a shame that the Palestinian leaders never just conceded they'd lost some land at each stage. But sadly, this is the case, and it makes sense that they'd be incensed at having had their land taken. In any case, we've gotta work with the situation on the ground.
When you say under attack, it sounds like they're besieged. They get a few suicide bombers by Islamist and radical nationalist groups, and a few rockets which very rarely hit anybody. In retaliation, they drop bombs, killing thousands of people, and absolutely marginalise and dehumanise millions of people. This is not some even conflict, Israel has by far the upper hand.
What I think they should do is cease encouraging settlement in the West Bank through tax breaks, cheap housing etc (but they shouldn't withdraw). They should negotiate much more practical security measures, which actually maximise security. They should stop bulldozing the homes of Palestinians, stop taking their lands away from them. This would make the foundation for a real peace process. I can't see it happening though, which is a real shame.