SB 11.21.29-30

te me matam avijñāya
 parokṣaṁ viṣayātmakāḥ
hiṁsāyāṁ yadi rāgaḥ syād
 yajña eva na codanā
hiṁsā-vihārā hy ālabdhaiḥ
 paśubhiḥ sva-sukhecchayā
yajante devatā yajñaiḥ
 pitṛ-bhūta-patīn khalāḥ
Synonyms: 
te — they; me — My; matam — conclusion; avijñāya — without understanding; parokṣam — confidential; viṣaya-ātmakāḥ — absorbed in sense gratification; hiṁsāyām — to violence; yadi — if; rāgaḥ — attachment; syāt — may be; yajñe — in the sacrificial prescriptions; eva — certainly; na — there is not; codanā — encouragement; hiṁsā-vihārāḥ — those who take pleasure in violence; hi — indeed; ālabdhaiḥ — which have been slaughtered; paśubhiḥ — by means of the animals; sva-sukha — for their own happiness; icchayā — with the desire; yajante — they worship; devatāḥ — the demigods; yajñaiḥ — by sacrificial rituals; pitṛ — the forefathers; bhūta-patīn — and the leaders among the ghostly spirits; khalāḥ — cruel persons.
Translation: 
Those who are sworn to sense gratification cannot understand the confidential conclusion of Vedic knowledge as explained by Me. Taking pleasure in violence, they cruelly slaughter innocent animals in sacrifice for their own sense gratification and thus worship demigods, forefathers and leaders among ghostly creatures. Such passion for violence, however, is never encouraged within the process of Vedic sacrifice.
Purport: 

The Vedic scriptures sanction occasional animal sacrifice to satisfy cruel, low-class men who cannot live without the taste of flesh and blood. Such concessions, however, are restricted by rigorous obligatory rituals and are meant to gradually discourage animal killing, just as the exorbitant cost of a liquor license restricts the number of retail outlets selling alcoholic beverages. But unscrupulous persons misconstrue such restrictive sanctions and declare that Vedic sacrifice is meant for killing animals in order to enjoy sense gratification. Being materialistic, they desire to attain the planets of the forefathers or demigods and thus worship such beings. Sometimes materialistic persons are attracted to the subtle lifestyle of ghosts and worship ghostly creatures. These methods constitute gross ignorance of the Supreme Personality of Godhead, who is the actual enjoyer of all sacrifice and austerity. The demons perform Vedic sacrifice but are inimical to Lord Nārāyaṇa, for they consider the demigods, the forefathers or Lord Śiva to be equal to God. Although understanding the authority of Vedic rituals, they do not accept the ultimate Vedic conclusion and therefore never surrender to God. Thus false religious principles flourish in the demoniac societies of the animal killers. Although in countries like America people outwardly profess to be followers of God alone, actual worship and glorification is offered to innumerable popular heroes such as entertainers, politicians, athletes and other equally insignificant persons. Animal killers, being grossly materialistic, are inevitably attracted to the extraordinary features of material illusion; they cannot understand the real platform of Kṛṣṇa consciousness, or spiritual life.