Continuity mistake: When May says, "It looks like Treecko might be feelin' a little weird around all our other Pokémon," there is a tree nearby, but in the next shot, there is not. (00:00:40)
Revealing mistake: As Seviper slips back into the bush after Torchic trips on its tail, the end of its tail is cut off. (00:03:16)
Revealing mistake: When Ash and his friends run into the Pokémon Center, a line is briefly layered over them. (00:07:06)
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.