There is a fine line here. Having read the article in the link, I think this guy Wolf was on the wrong side of the argument - but for technical reasons, not based on the underlying legal principle.
From the description of the tape, no one gave him an interview and the tape was posted publicly. Unless he edited out an interview in which someone identified himself as a perpetrator of an actual crime, Wolf's action would not have fallen under the usual "confidentiality of source" immunity. But even if he taped an interview in which someone confessed to 50 crimes, it is useless in court because the statement wasn't made under oath. If Wolf didn't himself witness or videotape the commission of a crime, then he is right in that the government was overstepping its bounds. The principle he stated is correct.
His status as a member of the press might be in question but the idea of freedom of the press absolutely depends on his ability to refuse to name his sources. If he gets an interview with someone and that interview contains information that would support the arrest of the interviewed, there is an issue to consider. If the journalist is seen as an extension of a law enforcement organization, he's not a journalist any more. He's a government snitch. (In the eyes of the person who just got arrested.) Why should anyone ever give him another interview if they know they will get arrested for it?
The USA has gone through cycles in which censorship of newspapers and coercion of source information have led to distrust of newspapers. As much as I believe that many news rags have become nothing more than sensationalist emotion-mongers preying on folks' baser emotions, there is still that concept of purity that must drive a wedge between government and journalists. Otherwise, you cannot believe in the integrity of what you read in the newspapers. (I mean, not just limited disbelief, but total disbelief.)
There is also the issue of a matter of degree vs. kind. If his videotape could lead to the arrest and conviction of an active serial killer or rapist or child molester, many states would allow coercing him to fork over the raw data. But in this case, that doesn't seem to apply. So let's just say that there is more than one issue involved here in the basic question of should he or should he not have turned over the tape.