Does that mean that otherwise indecent or vulgar speech, uttered during an open legislative session by either a legislator or a member of the public during an open session, would be protected?
If you mean the FCC couldn't fine because of it, I would think yes. No doubt the activities of a government or political body are important public events and of public interest. There already is a defamation protection for publishers running from the accurate recording of public events--if a lie is told in a public meeting or legislature, and a newspaper or TV station reports that, and is sued, they have an affirmative defense based on accurately recording public events.
I can guarantee that a similar line would be drawn from that defamation defense to a similar defense for broadcasting indecency contained in a political body's activities. For example, let's say during a Congressional session, broadcast on NBC for whatever reason, a member used the words "s--t" and "f--k"--both held by the FCC to be per se indecent in all contexts (a highly questionable ruling under Pacifica, but no matter). No doubt a session of Congress is of public interest and importance. If NBC decided to sanitize that session, to take out any indcent material, it would be reacting to a Commission rule that de facto censors a broadcast of the Congress--which immediately raises flags, because this is not only political speech, but also government speech.
There has not been, to my knowledge, a case where such a thing came up for review--not do I know of a Commission file for such a broadcast. Probably because the FCC knows that such a fine would be immediately appealed, and probably to the Commission's detriment. It is without question that Supreme Court precdent and First Amendment jurisprudence gives the most protection to political speech--even political speech that contains otherwise indecent material. Though Justice Stevens in Pacifica distinguished Cohen v. California (1971) (the "f--k the draft" jacket case), faced with the Commission fining for what really is political speech of the most protected kind--spoken by government officials--I can be certain that Cohen would control, and not the Pacifica rule.
As to your other question, broadcast "censorship" if they cut away from an official government body's meeting or activities--no, it would not be censorship, necessarily, because the government cannot tell them to carry certain programming. I understand how you could get that idea from the Senate Committee's Report statement from 1948, but it does not require a station to carry any programming in its entirety. However, should a station choose to do so, I'm fairly certain that the station could not, out of fear of an FCC fine, censor an official government proceeding or sanitize official government speech. The stations are free to join and disengage from government proceedings without any harm--it is a programming matter. But having taken the step of broadcasting proceedings or airing a political ad, the station may not censor, delay for content, or sanitize for content that political speech.
Remember, no station is required to accept political ads or air political proceedings, but once they do so accept, they are required to follow the non-censorship laws (e.g., Section 315 of the 1934 Act or other applicable laws).
