Probably not obstruction of justice, since they didn’t prevent law enforcement officials from obtaining evidence. But very, very likely slander, and possibly incitement to riot, as well as most certainly an abuse of the public airwaves, and ample cause for the FCC to remove their broadcast license.
Networks don’t have or need ‘broadcast licenses’. Those belong to individual stations.
Certainly a case could be made that NBC meets the standard of ‘reckless disregard of the truth’ and is guilty of defamation and libel.