How could anyone be a pro about something that doesn't exist?
Isn't that kinda like me saying I am a professional when it comes to alien currency, bigfoot specific hair dye, or "I'm with Nessy" diving expeditions?
Listen to enough stories from those who "see ghosts" and you'll realize they're just a bunch of weirdo's who cannot figure out how or why something happened so they label it a "ghost encounter".