Conservatives insist that the Constitution guarantees freedom of religion, not freedom from religion, and argue against strict separation of church and state. Too often, though, conservatives seem to have a flawed understanding of what freedom from religion really entails and fail to realize that freedom from religion is crucial to religious liberty in general.
It is evident that a person misunderstands the concept of freedom from religion when they say that promotion of the idea is part of an effort to eliminate religion from the public square, to secularize America, or to deny religious believers a voice in politics. None of this follows from a belief that people have a right to be free from religion.
What Freedom From Religion is Not
Freedom from religion is not a demand that one never encounter religion, religious believers, or religious ideas at all. Freedom from religion is not freedom from seeing churches, encountering people handing out religious tracts on the street corner, seeing preachers on television, or listening to people discuss religion at work. Freedom from religion is not a demand that religious beliefs never be expressed, that religious believers never voice an opinion, or that religiously-inspired values never have any impact on laws, customs, or public policies.
Freedom from religion is thus not a social right to never encounter religion in public spaces. Freedom from religion has two relevant aspects: personal and political. On the personal level, a right to be free from religion means that a person has the freedom not to belong to any religion or religious organization. The right to be religious and to join religious organizations would be meaningless if there did not exist a parallel right not to join any at all. Religious liberty must simultaneously protect both the right to be religious and the right not to be religious at all - it cannot protect a right to be religious, just so long as you pick some religion.
What Freedom From Religion Is
When it comes to politics, the freedom from religion means being "free from" any government imposition of religion. Freedom from religion does not mean being free from seeing churches, but it does mean being free from churches getting governing financing; it doesn't mean being free from encountering people handing out religious tracts on a street corner, but it does mean being free from government-sponsored religious tracts; it doesn't mean being free from hearing religious discussions at work, but it does mean being free from religion being a condition of employment, hiring, firing, or one's status in the political community.
Freedom from religion isn't a demand that religious beliefs never be expressed, but rather that they not be endorsed by the government; it's not a demand that religious believers never voice an opinion, but rather that they not have a privileged status in public debates; it's not a demand that religious values never have any public impact, but rather that no laws be based on religious doctrines without the existence of a secular purpose and basis.
The political and the personal are closely related. A person cannot be "free from" religion in the personal sense of not having to belong to any religion if religion is made a factor in one's status in the political community. Government agencies should not endorse, promote, or encourage religion in any way. Doing so suggests that those who accept the religious beliefs favored by the government will, by extension, be favored by the government - and thus a person's political status becomes conditioned on their personal religious commitments.
What Religious Liberty Is
The claim that the Constitution only protects "freedom of religion" and not "freedom from religion" thus misses an important point. Religious liberty, if it is to mean anything, cannot merely mean that the state won't use the police to stop or harass adherents of certain religious ideas. It must also mean that the state won't use more subtle powers, like those of the pocketbook and the bully pulpit, to favor some religions over others, to endorse certain religious doctrines rather than others, or to take sides in theological disputes.
It would be wrong for the police to close synagogues; it is also wrong for police officers to tell Jewish drivers during a traffic stop that they should convert to Christianity. It would be wrong for politicians to pass a law banning Hinduism; it is also wrong for them to pass a law proclaiming that monotheism is preferable to polytheism. It would be wrong for a president to say that Catholicism is a cult and not really Christian; it is also wrong for a president to endorse theism and religion generally.
This is why freedom of religion and freedom from religion are two sides of the same coin. Attacks on one ultimately serve to undermine the other. The preservation of religious liberty requires that we ensure that the government not be handed any authority over religious matters.