Oh absolutely. I agree that the Christian heritage of white Australia ought to be taught. Just as other elements of our history and identity are taught, and the same way - as an academic observation of a point or points in time. It most certainly should not be taught as reality, or even given more focus than any other shaping factor in our identity and present culture.
And all kids in 'Christian' nations should be taught the origins of Christmas - especially those of European/British heritage. If they only ever hear the Christian version, they are being wilfully prevented from accessing their own ancestral history.