I was brought up in a "good family" too and not sure what that means just because you were brought up that way, you couldn't say No! I taught my parents how to say NO! It got to the point they couldn't tell anyone NO and in some regards, affected their lives negatively. Now they've learned to say NO and have no regrets.
The land is YOUR family's property. First dibs to FAMILY! Go tell your friend to hunt on his family's property and if he don't have any, he should grow up and learn to find his own places to hunt.
Here's an idea:
"Hey Joe, I have this problem and it bothers me, so don't take it personal. As you know we hunt on the same property that belongs to my family. We were kind enough to let you hunt it multiple times and once you even over-stepped your bounds when I told you not to hunt there and you still did. Regardless, things are going to change. I don't have much land to hunt, but it's expected that our little piece of property is reserved for family only. From now on you won't be hunting there. It bothers me to have to say that because we're friends, so don't take it personal. With that said, I would like to go out with you sometime and help you find other places to hunt. We've been friends for a while now, so I'm sure this little incident won't come between us."
Your friend is a big boy now. He can live with it and find his own places. The sooner you tell him, the quicker he can get on finding new grounds to hunt.
Sometimes situations like these are awkward, but if you were brought up in a "good family", then you know it's best to be truthful, honest and straight forward.
Good luck,
iSnipe