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 [...]
You're seemingly going into the realm of "we get all our news about Israel/Palestine from Al Jazeeraz" there, which is a shakey foundation from where to start the rest of the assessment.
There's various "if this and that then..." bits I wouldn't argue with, and you know where my sympathies lie, but here you definitely start your case off badly. In almost everything you say around this subject, I have to mentally adjust to account for your rather tunnel-vision views.
I'm going to give my answer to the question, by the way: When the persecuted overcompensate and become the persecutors, then that's no longer a matter of cheering on the underdog. The bullied kid who brings his dad's firearm into school and shoots the nasty kids (even
just the nasty kids, though it's rarely so neat) can still be a victim
as well as a newly arisen perpetrator. This doesn't mean it's acceptable, and there's other problems.
Ukraine attacking Russian territory isn't that, of course. It's more the "learnt to stand up for yourself" level of counter-bully behaviour (a fine line between trading punches as a deterence and going too far, which is why in an ideal schoolyard scenario it should not be allowed to have needed to go that far... real life geopolitics is both easier and harder to 'police' than with teachers/etc in that setup, though... harder to have problems migrate beyond the school gates, as there is no "beyond the school" territory where eyes cannot be kept on things, but we also have no real "adult authority figures" whilstsoever the highest global 'authority' is the UN. Better than the bad teacher ("...he'll just have to learn that the world is a tough place") or the one on the wrong track ("...all I know is that I never had fighting in my classroom until <victim> arrived, and every time I turn around it seems like he's the one in the middle of it"), but very much the ineffectual type who can't ever assert their authority properly.
The situation of Ukraine w.r.t. Russia land is so much different from Israel w.r.t. Palestinian territories that I don't think we could really imagine similarities here, so skip that. Let us instead look to what equivalents we might see. e.g. Ukraine regains tacit control over Donbass/Crimea and then marginalises these "Russian pocket" inhabitants (helped by those who weren't Russian enough either voluntarily or forcibly relocated over these last few years or so - which is still a difference from the Jewish (lack-of-)presence in Gaza/West Bank). Then it could be said to be punishing people just for being more aligned to another system. Then we might see Ukranian efforts to "do an Israel" to an equivalent degree.
Given that mere Russian heritage/identity/language was not really so much of a problem in Ukraine until-recently (hence why so many took it upon themselves to
stop identifying as Russian, in the light of increased Russian aggression... even the President... can you imagine modern Israel being led by someone of Palestinian/other-Arabic pursauasion?) the anti-Palestine part of the pro-Israel stance just was not so much seen in the Russia/Ukraine version. (Pro-Palestine and anti-Israel opinions, vis-a-vis arabic neighbours, may or may not have present in the Moscow-centric neighbours doing their equivalent alignment of attitude.)
So there's actually a very large reality gap between the current situation and reaching the equivalent of the middle-eastern situation. Which is not to say that they can go far in that direction before being (rightly) vilified. Actually commiting attrocities[1] against Kursk's population would be a step Ukraine should not take. Also clamping down on the Russian-heritage peoples such as the US did with its 'Japanese' citizenry in WW2. From all I've seen, Ukraine has not gone anywhere near that kind of thing (nor the level of "Ukrainians by Russians" acts taken by the Kremlin's forces and (puppet-)governances), and it should definitely not try to match that.
Goodwill by the Western powers
and a degree of due diligence against genuine threats (actual internal arrests/etc having happened) can both be maintained. Pushing down too hard on one side can disrupt the other, and it's in nobody's interest (on this side of the equation) to do that.
I would have no hesitation to say that if Ukraine acted like Israel, it might well deserve to lose Western support. But to even be in that position presupposes crossing the Rubicon long before that. Israel seems to have accomplished its situation by "boiling the frog slowly and over a long time" (plus relying upon 'Western guilt' to excuse putting the frog in the saucepan originally). This cannot happen with Ukraine in any sufficiently similar manner, at least not without a lot more future-history to pack in the necessary prerequisites. One hopes that this would pan out differently; firstly by predominating
at all against Russia, then continued to be nudged away from whatever Russia (internally) would have people believe that Kiev is capable of.
[1] "...unnecessary atrocities..." was one version of this phrase, though that would admit to the existence of "necessary" ones. "Unavoidable..." is also differently problematic. There
will be errors and generally unforeseen consequences of military decisions, though, for which judgement must have to be made after the fact.