You still haven't cited one source.
While the O.T.O. included, from its inception, the teaching of sex magick in the highest degrees of the Order, when Crowley became head of the Order, he expanded on these teachings and associated them with different degrees as follows:
VIII°: masturbatory or autosexual magical techniques were taught, referred as the Lesser Work of Sol
IX°: heterosexual magical techniques were taught
XI°: anal intercourse magical techniques were taught.
 Crowley, Aleister. Magical Diaries of Aleister Crowley, p. 241
or, e.g. http://en.wikipedia.org/wiki/Eroto-comatose_lucidity
read all the sources passages, in juxtaposition with this, and it won't be useless to understand the issue at hand.
if you really are practicing Kalachakra, you need to have no release or loss of semen whatsoever. Moreover, there is probably no division to be made in this respect between practitioners of the generation stage and of the complete stage. To state this clearly is probably better.
Now, as for the actual root downfall of discarding bodhichitta, this is talking about having the mind that wishes liberation through the bliss of orgasmic release ('dzag-bde grol-ba 'dod-kyi sems). As for this bliss of orgasmic release, some non-Buddhist traditions (mu-stegs-pa) assert that offering a homa fire puja of semen in the reality source of a woman pleases Ishvara (dBang-phyug, Shiva) and that through this one can achieve moksha, liberation. But, liberation doesn't happen like that. Therefore, specifically to stop this mistaken practice, the vow was made that if, with a mind wishing for liberation through the bliss of orgasmic release, one ejaculates one's constituent source energy-drops externally (phyi-rol-du khams-phong-ba), it is a root downfall. Usually, however, when one has and ejaculates semen, there is no thought of wishing liberation through the bliss of releasing it. Thus, it is not a root downfall.
still, the guy inspired a lot of good music e.g. led zeppelin and amebix
edit: i am not in any way advocating tantrism, especially black tantrism (of the sorts i've mentioned in this post before mentioning the dalai lama). having said that, tantric practices must always be carried out under the tutelage of a qualified teacher (guru) and require that one have a highly stable, normal and remarkable sort of character; sexual tantras, at least in buddhist traditions i am familiar, are typically the last stage/tantra and so are exclusive to very advanced practitioners (see, e.g.: six yogas of naropa