@OhCalmTheFuckDownMargaret Is that addressed to me?
Let's imagine that instead of "civilians being killed in other countries" we have "ugly buildings".
Now imagine person A has 10 buildings in mind that they know to be ugly. They think all of the buildings are just about as ugly as one another (this is an analogy for condemning a multitude of instances in which civilians are killed).
Then person B sits down next to them and begins extolling the beauty of one of those 10, let's call it building X. (This is an analogy for the opinion "civilians being killed by Israel in these circumstances, is justifiable").
Which building (instance of civilians being killed) will they discuss? Its obvious isn't it? They're going to discuss the controversial building, about which they have a different opinion. A conversation about one of the other buildings which both parties mutually agree is ugly, would be short, boring and rather pointless.
From person A's perspective, it is person B's inexplicable defense of building X's appearance that interests and animates them to explain and justify why the building is ugly. This alone is not evidence that they're prejudiced against some other aspect of the building, or that they are holding it to a higher standard (though these are both possible, it is also possible that they just think it's ugly for the very similar reasons they think the other 9 are). The principle reason they are driven to comment on that particular building's ugliness is because someone else is being vocal about it's beauty.
Scale up by millions of people on either side of the discussion on the righteousness of Israel's actions.