God, by His great mercy and holy dispensation, has allowed the use of things in creation, such as the animals and plants, for the sustenance and survival of man.
Indeed, one of the first acts He accomplished after Adam and Eve fell from grace and were cast out of the Garden, was to give them tunics of skins to cover themselves with, demonstrating that in this fallen world, sacrifice is acceptable, as long as it is done respectfully and in thanksgiving.
It was indeed Abel's offering of livestock which He valued above Cain's roots and vegetables.
God loves all of His creatures and all of His creation, but none greater than man, who was made in His image and likeness. Indeed, He made all of creation for man, so that man may be stewards over it and share in it with God.
God loves the beasts and the birds and everything which He has fashioned, but none more than His very children. "For don't you know you are worth more than many sparrows?"
And it is our nature to which the Word of God united with His divine nature, so that creation might be renewed and transfigured into the Kingdom of Heaven. It is mankind who God has bestowed the grace of sonship and heir.
Thus, God allows animals and plants to be used by man for food and protection.
Of course, the heavenly way is one without meat and the death of animals, for this is the life in the Kingdom which we aspire to and hope for, where the wolf will sit with the lamb. This is the holier and more angelic way.
However, if one makes this a reason to judge another person in this world, and to castigate them or accuse them, (when God Himself has allowed it and ordained it), deprives them of any spiritual benefit and voids any virtue they may have had in living such asceticism.
In this fallen world, (which has been corrupted by the permeation of sin and the death of everything in it), God, in His great mercy, allows us to use the plants and animals for our survival. Yet, we must do so in a spirit of reverence, mercy, and thanksgiving. In fact, in the Old Covenant, before Christ the Lamb of God came to take away the sins of the world, He ordered it, and in that same manner.
The Church fasts for many periods in the year, abstaining from meat and animal products, as a preparation and training for our life in the Kingdom and for the purification of our souls and bodies before we commune of the Divine Eucharist. But, never, at no time, have the believers in Christ taught strict vegetarianism for the faithful as the only means towards salvation, and those who put this yoke upon others create a new religion apart from the faith handed down by Jesus Christ.