my thoughts are, if you find an animal in the middle of a 50,000 acre ranch, it's no different than hunting somewhere with no fence be cause he's never going to see the fence anyway.

I'll start this by saying I'm a PH and have hunted extensively in both fenced and true wilderness areas and (IMO) it does indeed change both the hunting experience and the animal behaviour dramatically. I don't have any real problem with hunting large fenced areas for plains game, but personally, I choose not to hunt DG in fenced areas as it's simply not the same hunting experience for the client.

Animals in fenced areas are pretty much always habituated to some degree to sight and smell etc of both people and vehicles, whereas in true wilderness areas, they tend to respond differently to those 'triggers'

Going back to unfenced areas, once you've hunted an area such as the Zambezi Valley or even better, the Selous Game Reserve of Tanzania, you'll never be completely happy hunting a fenced area - even a very large one.