Bummer.
My spot i grew up hunting (really my uncle and my mom's BF's spot) got lost in Pennsylvania due to fracking. It was a legal things and it stuck.
If they knew you personally and knew you hunted there, then they talked themselves into not caring. and its more selfish or mean than not ethical.
i would ask the owner to not let them hunt now that he knows you still hunt there and have for years.

~c~