Are you allowed to perform a malefic sacrifice? If you are, then it seems like the Veda contradicts itself, since elsewhere it prohibits violence. If you are not, why not, given that such sacrifices are prescribed in the Veda?The question has been dealt with for centuries by Mīmāṃsā and Vedānta scholars in particular and it is further complicated by the fact that violence within sacrifices, e.g., the slaughtering of an animal victim within the Agnīṣomīya ritual, is agreed upon by everyone. Thus, it seems that violence is not always violence, or at least, that it is not always condemned. The following one is Veṅkaṭanātha’s way to make sense of the conundrum:

[Obj.:] Because [the prohibition of violence] is unrestricted, because [violence] is prohibited, violence which is repeated as the result [of a ritual, and not as its instrument] is a sin.
[R.: No, because] the prescription about a subsidiary (aṅga) blocks the general [prohibition of violence]. Also the inference is in this case wrong because it is invalidated, etc. |
Those who belong to Sāṅkhya say that there is a small flaw easy to be avoided if one favours this rite (the Agnīṣomīya). It is said in the Śārīraka that it is not so, because of the mention of what is beneficial for the animal || 78 ||

With the words Because it is unrestricted the [author of the verses (who happens to be the same as the author of the commentary, i.e., Veṅkaṭanātha)] said that the Śyena and the Agnīṣomīya are different, through the purification of the [violent] activity by means of the prescriptions and the prohibitions [regarding it], since it is established that the adṛṣṭa is reached at only through the Āgamas. The meaning is: Both in the Śyena and in the killing of the animal victim within the Agnīṣomīya one sees violence. An activity which has as result the detachment from the vital breaths is denoted with the word “violence” and this is common to both cases.

However, in the Śyena the violence is not prescribed, but rather obtained out of one’s desire. In fact in its case the sequence of prescriptions is “If one would inflict violence, he shall do it through the Śyena”, and not just “One should inflict violence”. And in the same way in the case of the [Śyena] the violence is obtained out of desire, therefore the prohibition “One should not perform any violence” is in its regard unrestricted. Therefore, the violence which has been repeated as the result [of the Śyena] is prohibited in this case, not the Śyena [itself], because [the Śyena] has been said to be something different, with [Kumārila’s] words “The Śyena is different [than violence], like a sword [is not the same as a slaughter]” (ŚV codanā 205cd) and because it has been prescribed. That he said with By contrast, violence is a sin. This means that this violence which is obtained because of one’s desire is an evil, because it is prohibited by the Sacred Texts. By contrast in case of the killing of the animal victim in the Agnīṣomīya, although there is violence, since [the killing] has the form of an activity resulting in separating [the animal’s self] from the vital breaths, the general rule “One should not perform any violence” is blocked throughout he specific prescription “One should kill [the animal victim]”. Since, when there is a specific prescription, the general prohibition is weaker, as it has its scope of application only when it regards something obtained through desire only.

Therefore (athāpi), the inference “The violence in the case of the Agnīṣomīya is not dharmic, because it is violence, like the violence inflicted on a Brahmin” is wrong, because it is invalidated by the Sacred Texts (āgama) and because it has limiting conditions (upādhi), this he said with the words The inference.

In this regard the Sāṅkhyas think so: “The prescription about the killing of the animal victim in the Agnīṣomīya says that the killing is a subsidiary to the ritual. But the sentence ‘One should not perform any violence’ encompasses also the violence within the Agnīṣomīya because the word ‘violence’ works without any restriction. And in this way  this violence is the cause of something evil but this is easy to be atoned (parihṛ-), since it is Vedic”. In this regard the confutation has  been said in the Śārīrakaśāstra: “Although the killing of the animal victim within the Agnīṣomīya causes a major sufferance, it cannot be said to be ‘violence’. In fact, there is [also] not violence when a physician, etc., cut or cauterise, etc., for the sake of heal a tumour, etc. Nor is the  scolding of one’s child or pupil by the parents, [teachers], etc. a form of violence. Only a violent act not conformable to the Śāstras and performed by someone causing much sufferance is violence. In this regard, by contrast, although there is separation from the vital breaths, there is no violence, because of the compliance to the Śāstra. Instead, there is protection (rakṣā), because through the interruption of the body of the animal victim, which results in evil, [the sacrifice] causes for that very animal the attainment of a a special body which is conform to the enjoyment of upmost pleasure”. Having in mind this all he said Because of the mention of what is beneficial for the animal. With the mention of the mantra ”You do not indeed die, nor are you injured, you go in the divine with easy paths” (na vā u etan mriyase na riṣyasi devāṃ ideṣi pathibhis sugebhis, ṚV 1.162.21, found also in Rāmānuja’s Gītābhāṣya).  it is said that the animal obtains a specific place.
This is here the different [view]: Some say that once one has accepted that the slaughter of the animal in the Agnīṣomīya is violence, the prescription “One should slaughter [the sacrificial animal]” blocks the prohibition “One should not perform any violence. Others, by contrast, do not accept that there is violence out of the Sacred Texts or the Recollected ones, because it is not violence, given that [the slaughter] is the cause of the fact that through a little sufferance a bigger happiness is obtained and given that it is said in the Sacred Texts that “You do not die, nor are you injured…”.

(Tattvamuktākalāpa, 5.78, my (preliminary) translation)
Thus, there are basically two options:

• the Śyena is prohibited, because violence in it is not prescribed and it is performed only because of one’s desire (whereas no one desires to kill a sacrificial animal, it is slaughtered only because of a prescription to do it)
• all violence is prohibited. This prohibition is superseded in the case of the Agnīṣomīya by a more precise prescription to the contrary.

The first solution seems to me suitable to be applied more in general to the universal problem of violence in religious texts (Don’t do it if you can detect self-interest in it).