It's probably the actual physical metal laryngoscope that is the cause of the throat pain, and not the tube itself. The laryngoscope is used to pry open the throat so the vocal chords can be clearly sen. It's not violent but there is significant force involved and a slight mistake can get a tooth knicked. This visibility is needed so that an air tube can be inserted between the vocal chords to secure the airway.

https://en.wikipedia.org/wiki/Laryngoscopy#/media/File:Macin...