I get tired of this crap too. I had a bird roosted one year. I got there early. Dude (I knew he knew the bird was there because I watched him from afar trying to call him in while he was going to roost) comes in and I let him know I am there. Unbeknownst to me, he goes 100 yds or so away where he thinks the bird is coming and sets up 2-3 decoys. Sun comes up bird gobbles, he starts calling. I thought maybe it was a hen. No way he didn't leave, knowing I was there. I am calling, and he is calling and I realize it is him. He is literally trying to duel with me to get the bird. So I called and shut up.... Bird came by me I shoot him, dude comes over and tells me it was his bird, because he roosted him... I explained that I watched him and where from and that I was watching the bird from a distance so as not to spook him, so I roosted him too. It's public land. I knew he was coming and beat him there. Therefore it is my bird to chase in my mind.
Last year I had two dudes come into a small block of woods, that I was hunting. I had shot a bird 5 days before. They were hunting nearby and I knew they heard me shoot. I parked walked about 2/3 the way in and stopped to check my phone to be sure I wasn't off course. I keep hearing this thumping noise and look up to see two guys walking at me with decoy bags bouncing off their legs... I told them I was there and they left, but they had to park where I parked to walk in. they knew it was a small area, and still went in.
This stuff happens a ton, but mostly during turkey season. During deer season, I have only had one minor issue. Most of the time they see you they move, but during turkey they just roll up on you.