Former Vice President of the Buddhist Society and Chairman of the English Sangha Trust, Maurice Walshe, wrote an essay called 'Buddhism and Sex' in which he presented Buddha's essential teaching on human sexuality and its relationship to the goal (nibbana).
In point of fact, the most difficult precept of all for nearly everybody to live up to is the fourth — to refrain from all forms of wrong speech (which often includes uncharitable comments on other people's real or alleged sexual failings!
Within Theravada Buddhism there are four principal transgressions which entail expulsion from the monastic Sangha: sex, theft, murder, and falsely boasting of superhuman perfections.
Worthless man, haven't I taught the Dhamma in many ways for the fading of passion, the sobering of intoxication, the subduing of thirst, the destruction of attachment, the severing of the round, the ending of craving, dispassion, cessation, unbinding?
[7] While those aspects were a popular target of criticism and satire as charge of moral corruption, both "by Japanese who often were ideologically hostile to Buddhism themselves or by Western observers inclined to view Buddhism as an obstacle to Christian missionary success in Japan", as well as other orthodox Buddhists, some adherents to this lifestyle sometimes claimed it to be actually part of their religious practice.
[7] As such, there were currents of local esoteric Buddhism, possibly influenced by non-Buddhist folk tradition, that valued sexuality positively.
[7] The Japanese deva Kangiten, a Buddhicized form of the Hindu god Ganesha, was considered sexually symbolic, being represented as dual figures embracing.
[7] It received a wide worship, especially among geishas and people in the business of pleasure, and its esoteric sexuality meant its image had to be usually covered from public eyes.
[8] The 12th century saw the rise of the infamous Tachikawa-ryu sect, an extreme tantric sex school where human skulls and emission of sexual fluids were used in ritual, for which they were later persecuted and suppressed by mainstream Buddhists.
[9] Finally, even in non-tantric Buddhism, influential 15th century monk Ikkyu preached for sex and love as valid ways to reach Enlightenment.
In Everyman's Ethics, a collection of four specific suttas compiled and translated by Narada Thera, it is said that adultery is one of four evils the wise will never praise.
[13] Within the Anguttara Nikaya on his teachings to Cunda the Silversmith this scope of misconduct is described: "...one has intercourse with those under the protection of father, mother, brother, sister, relatives or clan, or of their religious community; or with those promised to someone else, protected by law, and even with those betrothed with a garland" (etc.- child/underage) [14] Bhikkhu Nyanamoli has provided an English Translation of the Majjhima Nikaya 41, "He is given over to misconduct in sexual desires: he has intercourse with such (women) as are protected by the mother, father, (mother and father), brother, sister, relatives, as have a husband, as entail a penalty, and also with those that are garlanded in token of betrothal.
[18] The dominant Gelug sect of Tibetan Buddhism holds that sexual yoga as an actual physical practice is the only way to attain Buddhahood in one lifetime.
The founder of the sect Tsongkhapa did not, according to tradition, engage in this practice, but instead attained complete enlightenment at the moment of death, that being according to this school the nearest possible without sexual yoga.
[20] According to the Pāli Canon and Āgama (the Early Buddhist scriptures), there is not any saying that same-sex or opposite sex relations have anything to do with sexual misconduct.
[27] Some Theravada monks express that same-sex relations do not violate the rule to avoid sexual misconduct, which means not having sex with someone underage (thus protected by their parents or guardians), someone betrothed or married and who have taken vows of religious celibacy.
For them, the Vinaya (code of monastic discipline) bans all sexual activity, but does so in purely physiological terms, making no moral distinctions among the many possible forms of intercourse.
[31] Some Tibet Buddhist leaders like the 14th Dalai Lama spoke about the restrictions of how to use your sex organ to insert other's body parts based on Je Tsongkhapa's work.
[32][33] However, the Dalai Lama has repeatedly "voiced his support for the full recognition of human rights for all people, regardless of sexual orientation."