Continuity mistake: When the inspector crashes against the band of musicians, the mess on the floor differs between the first shot and the one following.
Continuity mistake: After Isabelle recites the poem, the Inspector's head position doesn't match between the front and back angles.
Continuity mistake: When the kids are reading in the library and the author shows up, the kids flip all the pages and then the book appears pointing upwards or downwards.
Continuity mistake: When the inspector first approaches the flower girl, a luggage porter passes behind him. When the angle changes, the man is meters behind, repeating his previous movements.
Continuity mistake: After Hugo and Isabelle see the picture of the moon printed on the book, their hands alternate between being on the book, to away from the book, between angles.
Continuity mistake: When Méliès shows up after the projection, the film suddenly disappears from the reel.
Continuity mistake: After Frick gives the Dachshund, the Inspector looks at his watch and puts it in his pocket. When the angle changes, he is looking at his watch again and repeating all previous movements.
Continuity mistake: After Hugo's been saved by the inspector, he holds onto the automaton while being threatened by the cop. Méliès arrives and shouts, and for a brief moment the way Hugo holds the automaton completely changes.
Continuity mistake: The first time the doberman dog chases Hugo, it enters a hallway and skids. The passers-by behind differ between shots.
Continuity mistake: After Tabard shows the movie, he raises up twice.
Continuity mistake: When Hugo gives Mrs. Méliès the drawing, her hands change positions between the wide and the close-up angles.
Continuity mistake: Position and number of drawings on the bed in Mr Méliès' house differs between shots.
Continuity mistake: When Frick brings the Dachsund, the bag on the chair changes positions between shots.
Continuity mistake: After the automaton stops, Hugo slouches on a sofa. His position differs completely between one frame and another.
Continuity mistake: In the scene where the automaton stops drawing in Hugo's lair, in a close up there is a mysterious red spot on our right of Hugo's chin, but in the rest of the movie the spot is gone.
Answer: He's not making it a point to chase down random children - he's like a security officer at an airport. It's his job to apprehend thieves and troublemakers and keep the station safe, and he only threatens to send children to the orphanage if they don't have parents for him to return them to. Also, it's implied once he finally apprehends Hugo that his particular harshness toward orphans (and most of his character flaws in general) is due to apparently having been one himself. He spells out the kinds of lessons he was forced to learn by growing up without a family, explaining how he became so cold, bitter, and antisocial.