British TV Networks Banned the Episode “The High Ground”
Star Trek once (accidentally) advocated terrorism in an episode of ‘TNG’ called “The High Ground.” The episode dealt with the complexities of terror, and Data tried to bring it home to the audience by referencing our past (and future), by claiming Ireland is unified in 2024 after a massive terrorist attack.
Source: Doux Reviews
Unsurprisingly, British TV decided to ban the episode before it even debuted in 1990. It never actually aired an unedited version until much later, in 2007.