Not cool or neighborly. I would have a talk with them about it.
if they don't move it I would make it my deer/hog cleaning station.
Couple of boys did this in Concho last year and the GW made them move the gut piles because of "hunter harassment". Careful on how you proceed.
Talk to the neighbor and the owner. We talked to a few of ours and they relocated the stand to keep the trajectory from coming onto our property but never mentioned hunting their property line. They own up to the fence line just like everyone else.