Scientists often uncover truths that are politically inconvenient for whomever is in power. Which doesn't make it any less saddening that this sort of thing goes on. The Times has the full story.
The [current] administration, [former Surgeon General] Dr. Carmona said, would not allow him to speak or issue reports about stem cells, emergency contraception, sex education, or prison, mental and global health issues. Top officials delayed for years and tried to "water down" a landmark report on secondhand smoke, he said. Released last year, the report concluded that even brief exposure to cigarette smoke could cause immediate harm. ... In his testimony, Dr. Carmona said that at first he was so politically naive that he had little idea how inappropriate the administration's actions were. He eventually consulted six previous surgeons general, Republican and Democratic, and all agreed, he said, that he faced more political interference than they had. On issue after issue, Dr. Carmona said, the administration made decisions about important public health issues based solely on political considerations, not scientific ones
While it's clear that the current administration has a zeal for distorting scientific findings that has not been matched in recent history, it's also clear that it hardly has a monopoly on the practice.
Each [Surgeon General] complained about political interference and the declining status of the office. Dr. Satcher said that the Clinton administration discouraged him from issuing a report showing that needle-exchange programs were effective in reducing disease. He released the report anyway. Dr. Koop, said he had been discouraged by top officials in the Reagan administration from discussing the AIDS crisis. He did so anyway. All three men urged major changes in the way the surgeon general is chosen and the way the office is financed.