Well I think he's referring to humanism, not atheism. Humanism is a bit broader than lack of belief in deities; while as originally formulated it is not dependent on theism, it is something that a lot of liberal theists would have no malfunction with.

I don't know if he's right about a paucity of emphasis on love in humanism. It may be true, at least from a certain perspective, as it leans more empirical and less intuitive, and some people could take that as too unemotional or something.

If love is nothing more than understanding that the interest of others is part of your own rational self-interest, that doesn't sound very soaring or transcendent or selfless, but I do feel like it covers the territory without introducing maudlin sentiment as a necessary part of the concept.