While this may be true, why would you? If you are abiding by the law, the warden is on your side and an attribute to your land.
one obvious reason would be disturbing crops. some wardens prefer wheelers to walking and if you're going where the people are, that means they might just go tearing up freshly planted fields or fields with delicate crops, ruining a portion of your harvest. other reasons are that some wardens, pic a spot they like and frequent it, just like hunters, and if people are constantly being accosted by the same warden having to take time out of their hunt to provide ID and permits, then odds are they'll decide to hunt somewhere else. last time I checked, most farmers don't enjoy deer, at least in my region. if nobody is hunting your land because of a rogue GW, then something should definitely be done.
then there are the rich people that seem to enjoy buying large stretches of land for the sole purpose of not letting anyone else on it...seems to be a practice that is increasing in popularity in my area as well....
... and then there are the guys that have whiskey stills, pot plots, and meth labs scattered through the woods, but I don't care about their reasoning. and for the most part, I do agree and if a farmer does have a problem with poachers tearing his fields up and leaving his gates open and all manner of things, sure, by all means any game warden would be your best friend and probably welcomed to dinner if he caught the perps, however, as a landowner, it should be within your purview to bar anyone, no matter the badge they wear, from their property.
EDIT: we all have the right to own guns, some people see no reason why you would ever need one and that is their prerogative, however that does not remove their right to own one. same can be said for any of the amendments in the bill of rights, some people never have a need to exorcise them, however it does not change the fact that they are entitled to them.