I feel more than a bit under-qualified to comment on Un chant d'amour. I know little about LGBT cinema and nothing about Jean Genet, outside of what I've read following my viewing. Despite my ignorance, Un chant d'amour speaks on a very basic level that needs no research to understand. Banned as obscene and pornographic, the 1950 short film was smuggled to the United States in pieces, hidden in a traveler's clothing.
Un chant d'amour is erotic, but not arousing. (at least, not to me) It vividly communicates love and lust in a way that crosses sexual boundaries. I may not share Genet's love of the young actor, but I understand it, at least in part.
For those interested in the intellectual context, jim's film website has the best essay I could find on the film.
You can view it in its entirety for free online at http://www.ubu.com/film/genet.html
Un chant d'amour is #542 on the Top 1000 Films listTop 1000 Films list I’m working on. I’ve now seen 353.