Apple TV 6.1 update makes it easy to hide unwanted channels
Previously, you would need to navigate to Settings, then go through the list of available content sources and hide them. Now, all you need to do is highlight an icon on the screen, then press and hold the select button until the icons start to jiggle. Select the channel you want to hide, then hit the Play/Pause button to bring up the options, then press Hide. To undo this, simply go to Settings > Main Menu, then select the desired channel.
If you have your Apple TV set to update automatically, then you're set. To update manually, go to Settings > Software Update, then select Update Software.