Read up on the wikipedia definition of doxxing. It states plainly - it can be done from public databases or from social media, and that the goal is often to shame someone. This fits 100%. Otherwise you could argue that "it's not doxxing, I just went through this guys comments and he slipped up and said that he lives in X city, then posted a photo that let me triangulate his exact location in the city from landmarks". It is doxxing and a criminal act.