I'd say the basic position, without trying to start a big argument, is that regardless of historical grievances, Israel exists and is not going anywhere. That doesn't mean that its oppression of Palestinians is justified or that settlements in the West Bank aren't counterproductive to peace, or that they haven't committed terrible atrocities.
Be that as it may, none of that can ever excuse what happened three weeks ago. No amount of legitimate grievances can ever justify intentionally slaughtering hundreds of innocent civilians, and given that those attacks were explicitly organized by Hamas, who has the violent destruction of Israel and murder of its citizens as an explicit goal, Israel is justified in eliminating Hamas from ever being a threat again.
That does not mean that they have the right to just flatten Gaza and murder all its residents, which, it needs to be said, it easily could do and is not doing. However, while they certainly could be doing much more to protect the lives of Gazan citizens and should be criticized for not doing so, their fundamental aim of eliminating Hamas and forcibly de-militarizing Gaza is legitimately justified.
Ultimately, a two-state solution is the only realistic path towards some kind of peaceful co-existence, and that is impossible when you have a party like Hamas that is expressly opposed to the existence of Israel and takes action to indiscriminately murder its citizens. Again, that doesn't mean that Israel hasn't also done objectionable things as well, but what it hasn't ever done is drive the IDF into Palestinian villages and start shooting every man, women, and child they see.
Essentially, I support actions that make peace more possible and oppose those that don't. There is no world in which Hamas is part of a productive path to peace. Similarly, I'm also extremely opposed to West Bank settlements and have next to no sympathy for the people that voluntarily move there. They only really began in earnest once Likud gained power, and Likud is also a party that has no real interest in moving towards peace (though thankfully, they're absolutely toast once the fighting is over). However, the lands that were attacked three weeks ago have never been claimed by any Palestinian government and have been recognized as Israel's since 1949.
That's roughly the general liberal pro-Israel approach I see. Likud is bad and needs to go. Israel does a lot of bad things and needs new government (a sentiment shared by a good half of Israelis). Hamas are literal terrorists and absolutely have to go. If you have any genuine questions to ask that isn't just accusing me of being a genocidal maniac, I'm all ears.
