It seems that only certain factions of the Essenes believed that animal sacrifice was not permitted nor an original part of the Law. We know virtually nothing of the early Nazarenes especially to say whether they were allied with this particular faction of the Essenes.
This from an Essene essay on Yeshu and the Nazarenes about how St. Paul overwrote Yeshu's vegetarian teachings, sanctioning animal sacrifice and the eating of animal flesh:
There was an ancient Jewish religion which was very mystical, high and noble. It was a very evolved form of religion, rooted in respect and care for all of creation. This ancient Jewish religion was both very esoteric -- as evidenced by its Kaballah mysticism -- and yet very practical, as evidenced by its emphasis on daily lifestyle disciplines, ecology and communal economics. It was also VERY VEGETARIAN: not only was animal sacrifice forbidden, but so was the eating of animal flesh absolutely condemned. War and slavery had no part in this nonviolent religion. Women were the equals to men; women were entitled -- in fact, encouraged-- to participate in the Priesthood. This Priesthood -- called "The Priesthood of Melki Zadek" -- was governed by God via good angels and the divinely inspired BOOK OF THE ETERNAL COVENANT. Their original founder was Enoch; later, Moses led a major remanifestation of their movement. THIS ENLIGHTENED ANCIENT JEWISH RELIGION WAS KNOWN AS "ESSENE NAZARENE JUDAISM".
But Essene Nazarene Judaism was not the only form of Judaism. A violent, flesh-eating form of Judaism based on bloody animal sacrifice became the dominant religion in Israel. The nonviolent, vegetarian Essenes were persecuted by the animal sacrifice cult. Both forms of Judaism expected a Messiah: the sacrificial cult expected the Messiah to be a warrior king; the Essene Nazarenes expected a Messiah of Peace, a spiritual King. And so it was that the Messiah of Peace, the spiritual King of Israel, came to earth through the Essenes; for it was the Essene scriptures and prophecies that proved true. And so it was that the Essene Nazarene Jews, practitioners of the authentic Judaism established by God through Enoch and Moses, BECAME THE VERY FIRST CHRISTIANS!....
The fall from original vegetarianism into flesh eating and then human sacrifice is described in The Covenant of Love (a version of the New Testament revised with help from the Dead Sea Scrolls and published as part of Upton Ewing's, The Essene Christ). We read:
"And God said to man: 'Behold I have given you every herb bearing seed and every tree in the garden... to you it shall be for meat....' But alas!.... The will of God was no longer obeyed. Divine principles were overcome by sensual desires.... The most sacred of trusts of all time was annulled by the lusts of the appetite, and the blood of an innocent creature stained the hands of man....
"The Tree of Life was rent with pain. Its leaves hung limp in sorrow, its precious fruits fell to the ground in rot, and its stench deplored the sickening deed....
"Fear and foreboding grasped the heart of every living creature. The bold became vicious and the meek fled in terror, and the carcasses of dead beasts became the abomination of carnal appetites....
"Farther and farther man strayed from the truth of God. More and more did his power of choice become dominated by greeds and lusts. Weaker and weaker became his will to resist the cravings of the senses. Greater and greater grew the separation between the way of God and the way of man. And the True Light was obscured by the denseness of man 's own maleficent designs, and he no longer recognized the Divine Presence. Man thereafter began to invent his own god or gods.... [at which point the demons set themselves up to be worshipped as gods.]
"They arranged a variety of lewd ceremonials and lurid dances to please the indulgence of a 'sensuous God'. They spilled the blood of virgins, of children, and of the gentle lamb and the faithful ox upon the temple altars to satisfy a lustful God."
While the last paragraph of the above excerpt is shocking enough -- dealing with human sacrifice -- Peter, in the Clementine manuscript, makes an additional claim; he declares that the demons not only instituted animal and human sacrifice, but even CANNIBALISM:
"... these bast**d men tasted also human flesh. For it was not a long step to the consumption of flesh like their own, having first tasted it in other forms."....
Jesus on vegetarianism; in the Essene New Testament we read:
Jesus said:
"Verily I say unto you, they who partake of benefits which are gotten by wronging one of God's creatures, cannot be righteous; nor can they understand holy things, or teach the mysteries of the kingdom, whose hands are stained with blood, or whose mouths are defiled with flesh.
"God giveth the grains and the fruits of the earth for food; and for righteous man truly there is no other lawful sustenance for the body....
"Wherefore I say unto all who desire to be my disciples, keep your hands from bloodshed and let no flesh meat enter your mouths, for God is just and bountiful, who ordained that man shall live by the fruits and seeds of the earth alone."
Of course, Jesus practiced what he preached: he was himself a vegetarian. In The Gospel of the Holy Twelve, we read:
Jesus said:
"Of the fruits of the trees and the seeds of the herbs alone do I partake, and these are changed by the Spirit into my flesh and my blood. Of these alone and their like shall ye eat who believe in me, and are my disciples, for of these, in the spirit, come life and healing unto man."[/I]
In another verse of the same manuscript, Jesus declares:
"I am come to end the sacrifices and feasts of blood, and if ye cease not offering and eating of flesh and blood, the wrath of God shall not cease from you, even as it came to your fathers in the wilderness, who lusted for flesh, and they ate to their content, and were filled with rottenness, and the plague consumed them."
Immediately prior to the above quotations of Jesus, I listed two excerpts which prove Paul upheld the eating of animals; but what about meat sacrificed to idols? In his epistle called "Corinthians" (the same epistle in which he ordered women to keep their heads covered as a sign of submission to their husbands -- or have their heads shaved bald as punishment -- and never to speak in church), Paul wrote:
"As to eating meat offered in sacrifice unto idols, it makes no difference to God whether you eat such meat."
Compare the above words of Paul with the following words of Peter; in The Clementine Homilies, Peter declared:
"But you are still ignorant of this law, that everyone who worships demons or their idols, or sacrifices to them, or partakes with them of their table, shall become subject to them and receive all punishment from them, as being under wicked lords. And you who, on account of ignorance of this law, have been corrupted beside their altars, and have been satiated with food offered to them, have come under their power, and do not know you have been in every way injured in respect of your bodies. But you ought to know that the demons have no power over any one, unless first he be their table-companion; since not even their chief can do anything contrary to the law imposed upon them by God wherein the demons have no power over any one who does not worship them by being their table-companions in the eating of flesh.... But you, being ignorant of the foreordained law, are under the power of the chief of demons through evil deeds, wherefore you are polluted in body and soul, and in the present life you are tyrannized over by sufferings and demons.... If therefore, ye wish to be the vesture of the Divine Spirit,.... neither believe in idols, nor partake with them of the impure table...."
The rest of the essay can be found here:
http://www.essene.org/Yahowshua_or_Paul.htm