‘why is their kanaus limited to the learners that are not mekayim the being nehneh from their own work (which the chofetz chaim describes as at best midoh tovah) and not to the much larger groups of “earners” that are not mekayim the “aseh torascho kevah” which is, and always has been, the very basic fundamental obligation of every male Jew?’
Even if that were true, I think the answer is as follows: it bothers people more when a righteous person does something wrong than when someone less righteous person something wrong. If a person decides that he wants to work and not learn a word, that’s awful. But odds are, nothing I say can change that. My protest would be coming from the perspective of Torah and he already made the decision that Torah isn’t that important to him.
However, a person who is learning is obviously interested in doing the right thing. He is obviously genuine. And when people see a person who’s in kollel but not really made for it. He can’t really keep his sedorim because he’s not that good at it. His family is struggling because he’s not making a parnassah. His wife is forced to go out in the working world (possibly a violation of tznius- kol kevudah bas melech penimah) and he’s not learning enough to make it worth it. This person is trying to do the right thing, but is arguably doing the wrong thing. For this person, a macha’ah may work. For this person, if he realizes that full time kollel isn’t necessarily for him, and HKB”H wants him to be working, he would.
Or the flip side, is that this person knows he shouldn’t be in kollel but stays because he wants the prestige, or because of peer pressure, or because of simple laziness… so then he’s the worst of the worst because he’s using and taking advantage of Torah for his own personal gain… and this cannot stand.