Physicalism needs to be distinguished from atheism. Most Asian religions (at least those in China) would often meet the definition of atheist, but are not physicalist. ("Physicalism" replaces the older "materialism.") So when I self-identify as an atheist, it does not necessarily imply that I subscribe to Western notions of atheism, that assert that only physical processes (matter-energy) exist.

As far as the physicalist-atheist being admirable for living a moral life in spite of there being no philosophical foundation for doing so, I would suggest that they do so for the same reasons most religious believers do so--convenience, habit and childhood training.

Those who are truly immoral are rare (we call them sociopaths and it seems to be a mental abnormality). Very few people make moral decisions on philosophical or religious grounds, although they often explain or justify them after the fact by resorting to this sort of argument. The criminal is typically efficient at finding justifications within these systems--we all have to live with ourselves, and this includes living with our childhood indoctrination into cultural norms.