Why does Lama Atisha say those "observing pure conduct" shouldn't take (some) Tantric initiations?

In Lama Atisha's, A Lamp for the Path to Enlightenment he ends the teaching this way: > 64. Because the _Great Tantra of the Primordial Buddha_ Forbids it emphatically, Those observing pure conduct should not Take the secret and wisdom initiations. > 65. If those observing the austere practice of pure conduct Were to hold these initiations, Their vow of austerity would be impaired Through doing that which is proscribed. > 66. This creates transgressions that are a defeat For those observing discipline. Since they are certain to fall to a bad rebirth, They will never gain accomplishments. > 67. There is no fault if one who has received The preceptor initiation and has knowledge Of suchness listens to or explains the tantras And performs burnt offering rituals, Or makes offering of gifts and so forth. I interpret this to mean that people holding vows of conduct that are in contradiction to what is required in some Tantra (so-called taboo practices of sex, alcohol or other illicit activities) should **emphatically** not take those Tantric initiations. In Louisville, Kentucky in 2013 I heard His Holiness the Dalai Lama explain that monks should not be engaging in sexual tantric practices and that to do so is a defeat that will lead to bad rebirth. Was I misunderstanding something or is it not the case that Tantric practices that involve activities in contradiction to pure conduct should be avoided by those who hold vows of pure conduct? Do any schools of Tibetan Buddhism *disagree* with Lama Atisha's seeming prohibition? How about any schools of Vajrayana outside of Tibet?