Launchpad is an application that mimics what you see in an iPhone or ipad Home Screen and , as you know, can be used to er… launch applications. Just like on an iPhone or iPad, you can organize the icons, and you can remove them pretty much in the same way.
There is one important difference: in Launchpad, when you remove an icon you are NOT deleting the respective application, just removing it from the list. It is still in your mac and can still be launched in many other ways.
So click and hold on an icon, they start trembling and click the x - just like in the iPhone.
FWIW, this is not a bug. It certainly is worthless to have the icon there, but then you can put the icon for any application in Launchpad, and Launchpad itself is an application.