I have never hunted a high fenced area. Along with the high fence comes the high dollar price tag! But, a 10,000 acre ranch is roughly 15 square miles! Thats not exactly a "pen!"
It may not be as "sporting" as some might prefer. But as long as it is not just a small "pen" and its legal, these people are still paying licence fees, guns, ammo, bows, arrows and camo! Also, none of these animals qualify for the "book," so they are not hurting us! A small pen is a whole different story!