Still legal to film cops in Massachusetts

If there is one thing that really makes me angry, it is abusing your authority in order to bully people. In recent months a string of cases has been brought against people videoing cops while they perform their official duties.

In the Tiawanda Moore case I blogged about earlier, who was charged with "eavesdropping" after recording officers trying to convince her to drop a sexual harassment complaint, the jury saw through the bogus charges and acquitted her.

Last Friday, the US Court of Appeals ruled that the public has a right to videotape cops in public provided they do not interfere or obstruct.  The ruling is online.

What I would like to know is why prosecutors are so keen to bring cases against members of the public, taping cops who they believe in good faith to be abusing their office, and so reluctant to bring cases against Breitbart for his covert taping and selective editing smear machine. Any ideas?