>The mere existence of a fence on government property does not constitute an agreement to maintain said fence.
Can you imagine the sneering and hand wringing that would ensue in the comments if you tried to make such an argument about private property?
If a private landowner failed to maintain anything that was created by man (as opposed to nature) they'd say things like "public nuisance", "blighted", "antisocial" and all the other buzzword people of that bent love to use.
I don't really care what the standard is. If some standard is good enough to be worth legislating enforcing then it ought to apply equally to all land owners regardless of public or private.