Continuity mistake: When Pikachu agrees after Ash says, "Yeah, that's it!" his body is facing towards the rock, but in the next shot, it is not. (00:00:10)
Continuity mistake: When Ash says, "Uh-oh," Pikachu's pose changes between shots. (00:00:45)
Continuity mistake: When Brock asks why May would pass on her match at the Rustboro Gym, the back of her body is in front of a backrest, but in the next shot, it is not. (00:02:09)
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.