The "Shield" of Irresponsibility

Constitutional rights are a funny thing- not in the “ha ha” sense, but in the sense of strange. They are in the Constitution to prevent the government from infringing on the natural rights of citizens that make democracy possible.
Paradoxically, however, totally free, unrestrained exercise of these rights can lead to the downfall of democracy as easily as unrestrained restriction on the same rights.
Take, for example, the controversy about journalists protecting anonymous sources, even when facing a subpoena. Supporters of so-called “shield laws” say that they will protect the free speech of these sources. What they seem to forget, however, is that our rights also come with the responsibility to use them wisely and to face up to the consequences of misusing them.
If one of these anonymous sources were to, say, tell a journalist about the scandalous extra-marital affair of a local politician. Now, this might be relevant information to the upcoming election, but what if it turns out not to be true, or that this “source” used extra-legal methods to obtain his information? Should his free speech be protected then?
Or what if the source was an official who leaked top-secret information on troop movements to the media? Would that be an appropriate use of free speech?
True, there are instances where breaking the rules for a higher good might be appropriate, but if one is willing to do that, he should also be willing to face the consequences.
The problem with shield laws is that the distinction between a justified breach of trust (say, involving corrupt government officials) and an unjustified one (such as one that involves a false smear attack) is often blurred and/or hard (if not impossible) to prove.