This comes from a long discussion with Clara Zetkin, when she visited Moscow in 1920:
Freud’s theory has now become a fad. I mistrust sex theories expounded in articles, treatises, pamphlets, etc. – in short, the theories dealt with in that specific literature which sprouts so luxuriently on the shit heap of bourgeois society. I mistrust those who are absorbed in sex problems, the way an Indian saint is absorbed in the contemplation of his navel. It seems to me that the superabundance of sex theories, which for the most part are mere hypotheses, and often quite arbitrary ones, stems from a personal need. It stems from the desire to justify one’s own abnormal or excessive sex life before bourgeois morality and to plead for tolerance towards oneself. This veiled respect for bourgeois morality is as repugnant to me as rooting about in all that bears on sex. No matter how rebellious and revolutionary it may be made to appear, it is in the final analysis thoroughly bourgeois. Intellectuals and others like them are particualrly keen on this.
You might want to replace ‘sex theories’ with any number of intellectual fashions. I would love to have seen him at your run-of-the-mill intellectual conference.