Gannon Banned: Because the community attracts a more weapons-savvy playerbase, including (obviously) U.S. military personnel, misconceptions that would be ignored or upheld in other communities will get the poster scolded. The most common posts that attract this are requests for certain weapons, including: the MP5 (which is not used in the depicted units), the XM8 (a canceled project that's going nowhere), M9 pistols for everyone (pistols are rarely issued), knives as weapons (there's been nothing "combat" about knives since World War I), and the DesertEagle (which is not in use with any military unit, anywhere in the world, and is widely regarded as Awesome but Impractical in real life).
Military issue knives and bayonets are explicitly designed to be able to be used in combat.
Germans Love David Hasselhoff: Despite being a recruiting tool for the U.S. Army, this game has many players from Germany, the United Kingdom, Poland, and Italy, and the development team has taken measures to support players from other countries.
Hate Dumb: The game has been accused of trying to instill prejudice against Arabs. Which doesn't make any sense, as the enemies are clearly Eastern European in both appearance and linguistics, and the AKs they use in 2.x are of Romanian production. Then again, it's stupid people who haven't played the game.
Somewhat more justifiably, many with anti-war beliefs dislike it due to the fact that it's openly a military recruitment tool targeted at young people.
Paranoia Fuel: An arcade version is coming out soon. Don't be surprised if there are recruitment agents nearby as you play.
They Changed It, Now It Sucks: As with any multiplayer game, any change in gameplay causes a backlash from the "competitive" community. Since the game has gone through many changes and is now very different from its initial release, some players play a version older than the latest one.