The most famous among the experimenter lots was Shri Gopi Krishna. He was not in agreement that complete celibacy is important for a Kundalini seeker! What he maintained was that it is against nature to be a celibate. With such an expression, I wonder if he knew that everything that there is, is against nature then! Why would he feel different about his own Kundalini research institutions that quite didn't agree with nature? What is Prakriti/nature that is different from Purusha? While discriminating between things such as celibacy against nature, one has to say that prakriti itself goes against purusha, so to say. In one's search for purusha from the Sankhya philosophy, it is important to distinguish and give up longings towards prakriti. This would essentially mean giving up *natural* instincts too and being a celibate.
Coming back to what Gopi Krishna said... he also insisted though, that celibacy needs to be maintained (only) during the first phases of awakening the Kundalini. There, he seems to be in unison with the view that the Kundalini practice needs such a *discipline* and to quote him, "during this period, even one emission can be fatal. This has also been mentioned by Arthur Avalon in The Serpent Power".
Swami Sivananda Radha says, about the sect of Kundalini practitioners that believe in "anything goes" path, that most of the ancient views that suggest such things have been from the perspective of the male, while the female has to "bear the brunt" if there is a resulting offspring. Then she goes on to express that it seems contradictory to the aim for the female and it is difficult to believe that it would lead to a higher goal when the mother and child are ignored!
There is another interesting point that I would like to bring in here and that is of Osho! Osho started his research on death in his childhood. He had convinced himself that a person reaches an orgasm while dying! His findings are (supposedly) based on numerous visits that he lovingly made to deathbeds of many a people. Now, considering that semen gives life to an offspring, is it so difficult to agree that the loss of semen is exactly opposite, that is... death? I would prefer to say it is! Even Gopi Krishna said that during such time that Kundalini is awakened, what rises up the spine is sexual energy! How could losing of energy in acts of sex, then, be a means to raise the Kundalini?
This is precisely the reason why Kundalini, the one that raises the *consciousness* of a person, needs celibacy.
om tat sat