Having secularity promoted by law is a totally conservative notion- its a mixture of church(lessness) and state that just ain't cool.
OT, but this only holds true for the American multicultural conception of social liberalism. There are other conceptions of social liberalism that hold monoculturalism to be an ideal state, with the notion that all members of the society should create a public sphere where their private beliefs are not forced upon others, and/or a homogeneous front is presented to reduce prejudice. Examples of such civic secularity would include France and Turkey. Now, both of these examples are not without their problems. France has the problem that its "secular" civic ideology tends to include a default Gaulic cultural stance (including Catholicism), which in practice generally marginalizes non-Western immigrants. However, the "adopt-all-OUR-values-to-belong" problem notwithstanding, this framework provides for a civic body that ascribes to the same universal values regarding the role of church and state, the value of democracy, civic duty, respect for other's private beliefs (in principle at least, and as long as they don't invade the public or civic sphere), etc. A multicultural society doesn't impose these values, and leaves large chunks of the populace wholly free to want and encourage the imposition of state religions, want to expel non-members of a given chunk from the polity, and otherwise encourage sectarianism and intolerance. The notion of homeschooling as it currently plays out in the US would in particular be anathema to French monoculturalism, because it allows parents to choose to instill whatever civic values they please in their children, with no consideration of how this will affect the children's future interactions with society at large.
Both conceptions of liberalism have their flaws, and both demand a certain amount of misty-eyed idealism regarding widespread dissemination of fundamental values, either universal tolerance amongst the whole of the body politic, or strict unbiased neutrality on behalf of members and employees of government. However, again, this is off-topic. LCS focuses on the American conception, so a government that encourages secularism instead of striving for simple neutrality is encouraging irreligion over religion, and that violates American liberal multicultural values.