THE BRITISH BROADCASTING Corporation, which is intended to be independent of the government although it is state-owned, decided last week not to televise a news documentary on the conflict in Northern Ireland. The cancellation had been requested by Home Secretary Leon Brittan after objections were voiced by Prime Minister Margaret Thatcher. Neither had seen the program.

The broadcast includes an interview with Martin McGuinness, an elected member of the Northern Ireland Assembly, who is rumored to be chief of staff of the Irish Republican Army (a charge he denies). Mrs. Thatcher, who has herself been the target of an IRA bomb, understandably wishes to deprive the terrorists in Northern Ireland of publicity. But this hardly seems to us to justify establishing a national licy that closes the airwaves to alleged wrongdoers or to elected officials who oppose the government. British broadcast journalists are planning for a one-day protest strike this week to make just that point.

It would be simple enough for those of us on this side of the Atlantic to cheer the journalists on and reflect on the independence of our own press and the tolerance granted unpopular people and points of view in this country. But perhaps we should also use the occasion to take note once again of America's own little Bureau for the Exclusion of Unacceptable Ideas, or whoever it is that enforces our restrictions on certain foreign visitors. It's a good time to ask why principles universally accepted and fiercely protected in our society are not thought to be relevant to our immigration laws.

Anyone is free to say anything he pleases inside our borders, but foreigners whose views do not please our government may never get a visa to come here. The government has have denied entry to IRA leaders and to their enemy, Ian Paisley. It has refused to let NATO generals and Latin American poets visit. It has turned away a Canadian wildlife writer and Salvadorans at both ends of the political spectrum.

These people pose no danger to Americans or to our national security. We have no reason to fear their acts, but we let the world believe we are afraid to listen to what they have to say. It's the same kind of mistake the Thatcher government is making.