Continuity mistake: When Ash asks what they know about losing, the brown linings on Brock's jacket turn orange. This also happens when Ash runs out of the Pokémon Center. (00:18:12)
Continuity mistake: When Ash asks if Pikachu is ready for his challenge at the Dewford Gym, a poster behind a plant and a light go from being absent to being present. Also, the plant changes designs between shots. (00:00:03)
Answer: He is a good guy but just found himself in a bad situation when he worked for Lysander. He didn't want him to harm Ash and his Pokémon when he was trying to get the special bond between Ash and his Greninja to work. He does leave Lysander and go back to being a good person.