Many cultures historically have tortured consanguinamorous people to death

Margaret Williamson was told by the Kwoma that “if a man saw his son and daughter having sex he must immediately kill his son and cast his body into the bush.” Similarly, Grenville Goodwin found that among the Western Apache “if a close blood relative and clan-mate of the offenders, such as a brother, should actually see the culprits cohabitating or making love, he might kill one or both immediately.” One of the two cases recorded by Goodwin involved a man with two brothers and one sister. "One day he went off hunting. On his way home he came on one of his brothers out in the brush cohabiting with his sister. He shot them both."

[…] In the Apache case the chief of the culprits’ local group summoned a council and told them what had happened. “The culprits were then sent for or, if necessary, brought by force. They were flatly accused of their crime, and if they denied it, as they were likely to do, they were strung by the wrists from the limb of a tree, just high enough to permit their toes barely to touch the ground. Culprits who would not talk could be left hanging all day, and a fire might be built under the man. … Ordinarily the woman was not killed for the offense, because she saved herself by confessing. The man might be put to death whether he confessed or not.”

[…] Rafael Karsten [reports] that among the Jivo “incest and any illicit sexual intercourse is regarded with the greatest horror and severely punished by cruel ill-treatment. One case of this kind came under my notices when a young Jivaro Indian eloped with his father’s sister. All the male relatives of the family were pursuing the couple, and they assured me that if they got hold of them they would kill them.”

[…] Punishment for incest was as cruel in Ibo-speaking villages in Eastern Nigeria as among the Vedda and the Pashtun. M. M. Green found that “in the old days offenders would have been buried alive in the Agbaja market place, Orie Ekpa. This burying of them would purify and appease Ala [the goddess of earth and fertility].” Green’s informants “maintained that even now if such an offence were known to have taken place people would go secretly at night and cut a hole through the mud wall into the man’s house and kill him. He would then be placed at the foot of a palm tree, from which passers-by would imagine him to have fallen to his death.”

[…] With regard to the Cayapa, one of the native peoples of southern Brazil, Milton Altschuler writes, “Incest is generally viewed by the Cayapa as being particularly heinous. In the older days, it is asserted, anyone guilty of such a crime would be placed over a table which was covered with lighted candles, and then, slowly roasted to death.”

[…] When [the Jale caught and punished incest] […] the couple’s genitals were excised [i.e. cut from their bodies] and wrapped in leaves. [The genitals were then used in a ritual to purify the community of the couple’s sin.]

[…] The celebrated naturalist Charles Hose reports that while he was among the Murats, Klemantans, Kayans, and Ibans, “almost all offences were punished by fines only,” incest being the notable exception. “[…] If the guilt of the culprits was flagrant, they were taken to some open spot on the river bank at some distance from the house. There they were thrown together on the ground and sharpened bamboo stakes were driven through their bodies, so that they remained pinned to the earth. […] The other method of punishment was to shut up the offenders in a strong wicker cage and to throw them in the river. […]”

[…] Before they were colonized by the Dutch, the Toraja drowned incestuous couples or burned them to death. […] Our authority on the Miang Tuu, Herald Brach, tells us that “When incest occurred, the offenders were placed together in a large bamboo bubu [a kind of fish weir] and sunk in the sea. […]”

 - Arthur P. Wolf, Incest Avoidance and the Incest Taboos