The goal of a secular government is for people to check their religious beliefs at the door of the legislature. In the legislature they would discuss the limits that the government needs to set to maintain civil order.
People would define and pursue their ideals in their religion (and or philosophy of life).
The result of this classical liberal form of secularism was an increasingly tolerant society.
Radicalized secularism is a different beast. This starts when group of people decide to start forming their belief systems around secularism or science (a prime example is Marx's Material Dialectic which claimed to be a science). By claiming secularism as a tenet of their belief system, the adherents to this new irreligious-religion would take the stance that, since they hold secularism as a tenet of their beliefs, that they were excused from the need to check one's beliefs at the door of the legislature.
The ironical thing is that the people who take the paradoxical view of radical secularism is that they end up becoming less tolerant than the religions they despise, and end up trying to dictate their ideals and often become totalitarian in their actions.
I think secularism works best is a society where people recognize that they have a relgion. We all have ideals that we use on a personal level to guide our lives. Many of these ideals should be checked at the doorsteps of the Legislature so that we can create a workable society.