The news that mainstream candidates are negotiating for airtime on noncommercial stations was being criticized in some quarters last week as a "violation of the public trust." Hardly. Public broadcasting is partly funded by the government, but it is an independent broadcast entity and targets a population just as important to candidates as the unwashed masses. Public broadcasting strikes us as the perfect candidate for the free-airtime effort, which no more politicizes the service than it does commercial stations (the same can't be said for selling donor lists). If political speech is essential enough to require all stations to afford candidates equal time, we don't think public broadcasting should be exempt just because it is not allowed to charge for the time. That's why they call it noncommercial.