I think what you are asking more is when is someone labeled a poacher:

Then I guess at what point would I personally label or call someone a poacher:

When someone repeatedly and knowingly commits a smaller poaching act. Smaller acts that I would consider would be staying a few minutes latter then the law states, or the plug in your example.

Or when someone commits a flagrant act of poaching such as spot lighting, shooting from the road or vehicle (if not aloud in your state), taking over the limit, hunting on private land, setting up stands inside of restricted areas around houses and buildings, etc.