Do you think Ukraine would retain the nigh unconditional support of western governments if it treated Russians the way Israel treats Palestinians?
I think that if the Western public would believe Russia Today as much as they believe Al Jazeera, if Western media would reprint claims of Russians as facts as they do with HAMAS, if journalists and various NGOs would as actively seek (and\or invent) war crimes done by Ukrainians (there is a fair amount, believe me. War of this scale produces a lot, you just need to dig.) and report them again and again while mostly ignoring vile Russian war crimes... Yes, support would be lower. Way lower.
Furthermore, I expect serious problems if Ukraine should start winning big. Let's say the Kursk offensive will be unrealistically successful and we manage to encircle the city and start assaulting it. By the very nature of urban combat, even if Russians would not actively use human shields and evacuate some of the population, it would result in thousands of dead civilians. Also, Ukrainians are blessed by the fact... That Russian civilians do not resist. At least not in the way Palestinians do. If they start to do so - we will have to take steps that many naive peace lovers will see as war crimes\collective punishment.
Also, Ukrainian-Russian and Palestinian-Israeli wars are just different. If a sizeable population of Russians that live in Ukraine would start attacking random Ukrainians with knives, car-ramming and explosives, then there would be a response both from the government and from the public and it wouldn't be much different from what Israelis do. If the civilian population of the Kursk region did what civilian Gazans did - Followed Russian forces on February, entered Ukrainian territory looting, massacring raping, taking sex slaves, bringing Ukrainian corpses back home to dance on them while streaming it all on the internet, etc... Believe me, no order from above would keep Ukrainian forces polite and civilized.
PS. If we look at the radical segment of pro-Palestine supporters - they are already very pro-Russian. Palestinian + Russian flag is a far more common occurrence in any social network than Ukrainian + Palestinian