"How can I deal with a local gym cheater?"

#PokemonGO: So it's pretty obvious that a local player in my area is cheating. I play when walking my dog so I'm outside at public /non-residential areas in the morning and at night and I can clearly see that no one is there. There's a few stops along the coast where there's no cars/homes close enough to the gym so you have to be there on foot in order to interact with the gym. I took a gym down and put up my Pokemon, within 20 seconds it was being attacked and went down. This was morning and I could see no one around and there definitely wasn't anyone nearby except me and my dog. And this keeps happening.This player has maxed out Blisseys in every gym in my area, and any time someone takes a gym down he's almost instantly taking it down and putting a Blissey there. It wasn't making sense to me at first (I was honestly thinking is he following me?) because I was taking down gyms along this coastal path and not seeing anyone else. So he's clearly gym spoofing.What can I do about this? It's annoying that I'm out in the cold putting in the work and he's probably doing it all from home just cheating away. Can I report it to Niantic? Anyone know the odds they'll do anything about it? Thanks for your help via /r/pokemongo http://bit.ly/2HBwKPj