Through writing this passage, Igor Stravinsky is attempting to point out the inherent split between the musical conductor and the music that a conductor supposedly creates. He describes conductors as inferior to the music that they conduct, as not worthy to conduct it; he even accuses them of being a plague on otherwise musical concerts. Throughout this passage, Stravinsky vividly illustrates the seeming incompetence of the musical conductor.
From the very beginning, Stravinsky ties conducting in with the more impure elements of society. "Conducting" is, for him, in many ways "like politics"; politics is widely regarded as one of the most corrupt institutions in modern society. "Corrupt" is indeed the word to describe these people; they are described as existing more for the satiation of their own ego than for the benefit of the music that they profess to conduct. This is evident when Stravinsky proposes the following contrast: "The successful conductor can be an incomplete musician". According to Stravinsky, "greatness" is inversely proportional to musical ability; the more acclaimed a conductor becomes, the less capable a musician he must be. Stravinsky uses a fair amount of sarcasm to drive this point home, as when he points out that "a 'great' conductor …is very nearly the worst obstacle to genuine music-making".
Instead of music, conductors, it would seem, focus primarily on improving their social status. His career is "not dependent on [his musical skill] in any case, but on the society women (including critics) to whom his musical qualities are of secondary importance", as notes Stravinsky with a good deal of sarcasm and irony. Sarcasm and irony seem to set the tone for this piece, actually. Despite the fact that he is a conductor himself, Stravinsky seems to regret the status quo for conductors, and as such, he describes it in less-than-flattering ways. He probably wishes that conductors could be more important to music, but alas, they are not, and they are doomed to be demonized even more than they are already, at least within his writing.
Conductors, it would seem, are not merely egotistical parasites, feeding off of "the sun of a pandering public"; they are, indeed, diseases, infecting the very bands and orchestras that they "conduct". Stravinsky weaves in a continuing metaphor linking conductors with disease: They suffer from "ego disease", and they grow "like a tropical weed" in the limelight. The one purpose that conductors still do fulfill, conveying the emotion intended by a piece to a non-hearing audience, is carried out using "corybantics", wild, frenzied dancing often associated with either the mentally ill or with people trying to walk on hot coals. Stravinsky even goes so far as to encourage people "not [to] go to the concert" so as to avoid the disease of the conductor. Regardless of ones's point of view, Stravinsky does not paint a pretty picture of conductors.
Stravinsky clearly has a distinct distaste for conductors. He makes use of a number of pungent imagery techniques to vividly display his largely condescending opinion of all such people. And for each form of language that he uses, he makes sure that the corruption and antipathy towards real music that he sees from conductors is presented, precise and clear, for all to see.