OGB - I would be interested in hearing from a good faith Pro-Israel side of things beyond your good point already about supporting democracies, since most here fall on the other viewpoint.
I guess I should start by qualifying that, because I certainly do not believe we should be giving Israel any weapons or military aid while they're perpetrating abuses in Palestine. However, if worse came to worst and I had to pick to save one with the other being wiped off the face of the earth, I would hold my nose and choose Israel.
Pinning down the exact reasoning for that would take a lot of soul-searching, and I laid out a lot of potential factors in a longer post, but democracy and Western values come first.
The utter heinousness of the attack is another reason. In my mind, while I condemn both of them, I can see a sliver of daylight between firing a missile at a legitimate military target (or at least one that you've convinced yourself is legitimate) and killing innocent civilians and just straight-up butchering someone face-to-face at a music festival or in their home. I also see a difference between celebrating those attacks and tolerating them as a necessary (or, again, one that you've convinced yourself is necessary) evil.
Hardline laws like executing men for engaging in gay sex or pardoning rapists who marry their victims are disgusting, and create an environment ripe for human rights abuses.
Israel has never posed a threat to the United States, and acts as a partner against shared threats in the region, including providing us with intelligence in the War on Terror. Hamas is closer ideologically to ISIS and OBL than Israel is or ever will be, and I do not believe they would be inclined to cooperate in the same manner, while there's a non-zero chance they would cooperate in attacks against us.
These are just initial thoughts. It's hard. It's complicated. As Ph said, Israeli democracy appears to be failing. If that continues, then I trust my opinions will continue to shift.