For society to function well, there have to be basic levels of trust and cooperation, a respect for institutions and deference to common procedures. By deciding to unilaterally leak secret N.S.A. documents, Snowden has betrayed all of these things.
He betrayed honesty and integrity, the foundation of all cooperative activity. He made explicit and implicit oaths to respect the secrecy of the information with which he was entrusted. He betrayed his oaths.