Allegheny and the "Secular State"

Consider this excerpt from Justice Blackmun's Majority opinion:

The government does not discriminate against any citizen on the basis of the citizen's religious faith if the government is secular in its functions and operations. On the contrary, the Constitution mandates that the government remain secular, rather than affiliate itself with religious beliefs or institutions, precisely in order to avoid discriminating among citizens on the basis of their religious faiths. A secular state, it must be remembered, is not the same as an atheistic or anti-religious state. A secular state establishes neither atheism nor religion as its official creed. Justice Kennedy thus has it exactly backwards when he says that enforcing the Constitution's requirement that government remain secular is a prescription of orthodoxy.

Is a secular state neutral between religious citizens and nonbelievers? Should public displays and memorials reflect the pluralism of a  nation such as ours? Does a public square that contains only non-religious displays truly reflect the religious diversity of our Nation?