Freedom of Thought and Belief

The Court often says that freedom of thought and belief are protected by the constitution. But from what? How can a modern democratic government such as ours threaten freedom of thought and belief? We are not a Clockwork Orange kind of society, are we?

One commentator posed something like the following hypothetical:

"Suppose that the government conspired with the TV networks to include subliminal messages urging viewers to 'return the Administration to office' or 'to support laws recognizing same-sex marriage.' Would this action by government violate the First Amendment, or at least a broader principle of freedom of thought, belief and conscience underlying the First Amendment? "

If you think the subliminal messages are unconstitutional, what about more direct invasions of the minds of citizens? May government in Massachusetts require citizens to read a book supporting, say, same-sex marriage? May government in Mississippi require citizens to attend a showing of a documentary describing abortion as a form of unjust, legalized taking of innocent human life? May government require children to show up as a captive audience to be instructed and examined in the government's idea of common beliefs, common values, and common knowledge? In any of the above cases, should it matter if government conscripts its audience not by threat of prison, but by withholding governmental benefits from those who choose not to attend?

If we view the First Amendment as protecting freedom of the mind--of belief and thought--we might find ourselves arriving at some interesting conclusions about the propriety of various governmental programs.