Vishnu incarnates as the Buddha to teach and to end animal slaughter.
And in my village-Hindu estimation this is what's meant by deluding demons and leading them away from the Vedas. I think "demons" refers to the brahmins who lived by the letter of the Vedas and not by the real teachings or spirit. Not unlike Christ's issue with the Pharisees. In the Bhagavad Gita 2.42-43 Krishna says "Men of small knowledge are very much attached to the flowery words of the Vedas, which recommend various fruitive activities for elevation to heavenly planets, resultant good birth, power, and so forth. Being desirous of sense gratification and opulent life, they say that there is nothing more than this."