It is possible to remove some items from The Finder's context menu in the Keyboard preference pane, it is not however possible to remove the specific ones you have asked about, at least as far as I can tell. If you would like to try and remove some of the other items, go to System Preferences --> Keyboard and select the keyboard shortcuts tab. Select "Services" from the list on the left hand side and then scroll down to the "Files & Folders" heading on the left hand side. From here you can select which items to keep and which to remove. As I said, there is no option to remove "Burn" or "Labels" but at this point I don't think that is possible. I'll certainly keep searching for you though.