Perhaps I should have chosen a better descriptor than "low". I seem to have introduced a confusion.
Let me change the description of Christian's morality, which he describes as one of prizes and consequences as "first-form". That sounds better than "low", doesn't it? It's a "Do what I say, or else" morality. It's a law giver morality. It's a "Thou shalt not" morality.
Jesus changed the commandment morality base, to "Love". It's a positive message. Love God and your neighbor. Whatever you do to the least among you, you do to me. Live your life with love as your guide. Not Hell... not even heaven... love. That's the only law you need to concern yourself with.
It happens to be something that atheists and Christians can agree on. Caring for our loved ones, our children, friends, community, and country is enough to make us better people and, in our actions, indistinguishable from those who include God in their list.
Morality is a complex notion. I'm no expert but the problem with "first form" morality, the morality of laws, rewards and punishments is that no one can know all the laws. Christianity has 30,000 sects or something like that. Jesus, rightly in my opinion, offered an empowering alternative to his followers. Keep it simple. Act out of the love in your heart.
This is where I think Christian is mixed up. He has latched onto the punishment/reward aspect of Judeo-Christian-Islamic morality as the reason to be moral. It blinds him to the higher form Jesus spoke of. Atheists have ideals and feel love, it's a human thing. We can all find our morality in the exploration of our ideal.