One thing you might have missed, regarding reasons why so many people support a no-fly zone, is that a lot of people just aren’t thinking through what that actually means at all. Like, maybe you are so used to thinking about what your words mean that the inferential distance here is too great, but I think the thought process for probably a majority of poll respondents is something like:
All-out open war with Russia — that sounds scary
Doing nothing — that seems bad too
Aha, I hear about this “no-fly zone” and it sounds like kinda middle-groundy between those two things, so I guess I’m in favor of that! I think if you were to taboo “no-fly zone” and replace it with “US aircraft shoot down Russian planes, also US bombs Russian anti-aircraft emplacements in Russia, also US Navy ships sink Russian AA destroyers, etc etc” then you would see polled support plummet. So I don’t think that seeing high poll numbers for “no-fly” is really any evidence of the kind of nihilism you mention, just imprecise thinking. One piece of evidence for this is that if climate doomerism was responsible, you should expect to see the most left-wing/green new deal members of Congress pushing the no-fly zone, and you do not see this.
The unclear thinking is no excuse for the leaders who are pushing this line though, who should know better. I expect they are just playing politics, dishonestly pushing this knowing Biden will have to say no to it, so that they can accuse Biden of being weak.
I feel like, for certain coed social spaces, the cultural expectation of universal monogamy actually does (did?) a lot of work. If I (married man) am hanging out with some other married woman, we have Common Knowledge of each other’s unavailability. In my subjective experience, it breaks the attraction->desire link. And it’s desire that seems to add all the social tension, not attraction per se.