I agree that Buddhism is not a branch of Hinduism. However, I think it's important to understand that Gautama Buddha was born in a Hindu family and he was not satisfied with Hindu way of understanding the Ultimate or Bhramha and set out on his quest to find the answers. But then, since hindus are polytheists and very inclusive at the same time, they just worship every god and goddess out there as Vishnu's avatar. No wonder, when missionaries went to preach about Jesus in 17th 18th centuries, they even regarded Jesus as one of Vishnu's avatar and started worshipping him. The missionaries were somewhat frustrated because they could not completely convert hindus. I thought that was very interesting.. So, if ppl want to believe that Buddha was Vishnu's avatar, let them believe that. I don't think there's any harm in doing that.. why do you need to be so possessive about wise ppl??.. everyone can learn from them. Just my two cents!