atheism is part of hinduism. adiguru shankaracharya however through logic and debate sweeped all the existing atheist philosophies of his time. and all the atheist of that time became his followers/ it is rather childish to argue what is hinduism and what is not. Everything is hinduism and nothing is hinduism infact even the name hinduism is non existent in any scriptures. Hinduism doesn't say you cannot eat beef. it doesn't say you cannot kill cow. it categorizes everything into three qualities as you may know: 1. satvic: qualities of daya maya paropakar. for food it is something that is easy to digest, healthy, aromatic and gives pleasant feelings, coolness and peace to the atman. 2. rajasic: these are qualities like: jealousy, pride, greed, gluttony and too much involvement in pleasure to the senses. food involves too spicy, oily that gives you heartburn and digestion problems. 3. tamasic: this is worst quality like: killing, hurting others, sadism etc food involves stale and rotton food unpleasant smelling etc through out our life these qualities fluctuates. only yogis and sadhus are in steady state conditions.