The ideological terms where picked fairly carefully with an eye towards 'ideological soundness' and had multiple purposes. 'Rootless cosmopolitan' was an antisemitic dogwhistle, it was also part of a deliberate effort to shift to a more Russia-centric Soviet ideology. In a way it was also a Russian dogwhistle so tptacek was kind of right after all, completing the pedanticircle.
I regret (and did even at the time) using the words "dancing around" --- I was just waking up (let's not discuss the unhealthiness of "commenting on HN" being one of the first things I did after regaining consciousness) and even as I wrote it was thinking "this conveys more intentionality than I mean to".
So for that bit, I apologize! People still should aggressively avoid the term. I only saw this thread because I've been on a sort of comment bigotry scavenger hunt with "rootless cosmopolitan" as one of the items.
I wouldn't casually use it in English, though, precisely for the reasons you outline.
It was also quite informative to learn about this phrase and its nuances.
