So Buddha religion strictly forbids animal killing or flesh eating. That is real Buddha religion. Keśava dhṛta-buddha-śarīra, sadaya-hṛdaya-darśita-paśu-ghātam (Gītā Govinda, Daśāvatāra-stotra 9).
Now the Śaṅkarācārya's mission was because the whole of India under the patronage of Emperor Aśoka, all Indian people, they became Buddhist. Lord Buddha, he was incarnation of God, so he was very powerful. So śaktyāveśa-avatāra. So he converted practically the whole population of India, Buddhist. They gave up Vedic type of religion. Now this Śaṅkarācārya's mission was to reestablish again Vedic culture and stop this Buddha philosophy. Buddha philosophy later on deteriorated in so many abominable condition. Actually, it came down to the point of again animal killing under the name of Kāpālika. The Kāpālika process is very vicious—they kill their disciples, and so many things there are, the Buddha Kāpālika. It became a vicious religious system. So Śaṅkarācārya wanted to stop.
So now the Buddha philosophy flourished for temporary relief, for stopping the animal killing, and the Māyāvada philosophy also flourished to stop the Buddha philosophy. So both of them are asat-śāstra. Asat means emergency regulation. They are not for our eternal life. Eternal life, religion, or our occupational duty, is different. That is devotional service, eternal. In any condition, sa vai puṁsāṁ paro dharmo (SB 1.2.6). There are different types of religion all over the world. Each religion has got a certain motive to benefit the human society. So there are different types of religions, originally on some philosophical basis. So let them remain. We have nothing to bother or fight with them, because after all, every religion has got some good motive to elevate the person to a certain stage of understanding. They are called dharma, or religion.