One way to look at it is to think of the behavior itself as a type of enemy.
Despite Russia being the West’s adversary, so is Terrorism, at least ostensibly.
It could be like “Yeah we’re Ukraine’s ally, but we don’t condone terrorism so we’re going to warn”.
Note I have no knowledge of the specifics of this event other than the absolutely highest-level “there was a terrorist attack in a moscow theater”. Just discussing the “game theory” of why someone like the US or France might warn Moscow of a terrorist attack even while in a proxy war with Russia.
I mean, maybe that’s naively idealistic of me, but it’s a way to reason about whether or not to support it.
That is something I thought of, but withheld because I didn’t want to seem biased, and I don’t really don’t hold a lot of good faith in US foreign diplomacy.
It does make sense considering it’s the only real geopolitical angle they’ve begrudgingly worked together with in the last decade or so.
