just not sure I understand your point about "taking liberties"
What I'm getting at is that some individuals over-use public footpaths and do not (or cannot) see the potential conflict with legitimate users; if anyone challenges them, they get on their high horse and start shouting the odds, which does the rest of us no favours.
As I have already said, I feel that a lot of this attitude is born of laziness, lack of consideration for others and ignorance, wilful or otherwise.
When I started riding off-road about 25 years ago, I took the trouble to find out where I could and could not ride legitimately, with the help of a little reading and an OS map. It took about 10 minutes to establish the facts and to start planning routes on a map. I don't understand why people cannot do this now, especially now that information is so much more readily available.