> Well yes, but what if they support the initial terror attacks?
"What if" is the key phrase there. Can you jump into the minds of every Palestinian and know their likes, dislikes, motivations, level of support for Hamas? No, of course not; none of us can.
> Massacring dance festival attendants and people in their homes is not self defence, it is terrorism.
Absolutely agreed. But I'm not convinced what Israel is doing in Gaza is self defense either. There's certainly a self defense component to it, but cutting off electricity, water, and communications, and indiscriminate killing of non-combatants... well, none of that is self defense; those are war crimes.
Israel certainly has the moral right to defend itself against threats (existential or otherwise), but the response needs to be proportionate. I don't believe what they're doing is proportionate.
Summarily executing people for thought-crimes does not strike me as particularly aligned with basic humanistic and liberal values.
And tons of Israeli also support rather distasteful things, including before Oct 7, which has been widely documented. Some of these people are currently ministers (e.g. Ben-Gvir, Smotrich, etc.). And many Americans, and Italians, and $any_other_nationality. I don't want to play "tit for tat" here but only for Palestinians have I ever seen the "well, they support Hamas, so therefore it's not a big deal" line of reasoning.
> Well yes, but what if they support the initial terror attacks?
Even steel manning your position and assuming most of the women and children being killed (and worse) by Israel cheered the attacks (which we have no evidence is true) , no, actually, you aren't justified in massacring people just because they took pleasure in an evil thing that happened to you.
Massacring dance festival attendants and people in their homes is not self defence, it is terrorism.