You aren't doing anything "wrong". The inside of the pipe is rusted so the tubing is "trapped". You have to take a screwdriver or chisel and pry between the pipe and the tubing to "collapse" it. Then you can remove the tubing, but do not expect to have an easy time inserting a new piece, unless you ream the rust out of the pipe.
Side note; Obama, hopefully, in a year or so you will have competition for that name and icon.