Can a person be blamed for their thoughts?

Freedom of speech, let alone of thought, is a foundation of our society, written into our constitution to prevent the tyranny of the majority and allow a healthy intellectual discourse. But the actual practice of this supposed ideal, in which any idea, no matter how abhorrent it is to you, must be allowed expression, seems to run absolutely contrary to our instincts, to the point that we will openly attempt to make exceptions. Take pedophilia, for instance. The sexual abuse of children is, of course, a crime, and rightly results in prosecution. But on a number of forums, with Fluther by no means an exception, people have claimed that they would willingly kill the sick f*cks who even think of children in a sexual way; that they would willingly see pedophiles locked up for the crime of thinking disgusting thoughts. Now, to some extent this is rhetoric- I doubt that many of these people would themselves be willing to sign the bill into law or perform the execution by their own hand. But nonetheless, people seem willing to make a person’s private thoughts criminal, to apply the normative force of government and society to the ideas and emotions of a private citizen, when those thoughts become sufficiently repulsive to the conscience.

Taken out of the context of an impassioned defense of children against abuse, where such rhetoric might be appropriate, do any of you still feel that it is morally, ethically, or even pragmatically defensible for such an intervention to be made? Can society legitimately exercise a moral standard on its members, outside of the practical defense of their physical security? More philosophically, can a person legitimately be blamed for their thoughts? Remember, this discussion is not about pedophilia- that is simply a convenient example- so try not to rely solely on the argument that the government should intervene to prevent the potential harm of a child.