Lord
There's two sides to that argument though.
Farmers have a right to use the land for the purpose of, well, farming. Farming is not always "a pretty good deal" and if it weren't for farming I wonder where you think much of your food would come from? Although of course famers and landowners have to obey the law and keep rights of way accessible, ensure fencing is suitable etc. I have no time for farmers or landowners blocking access to public footpaths/bridleways.
However, as a landowner (horses, not a farmer although from farming family) I cannot tell you how infuriating it is when people trample all over the land without any thought or respect. I have lost count of the number of times gates are not shut, litter is left lying and the number of people who don't keep their dogs under control around livestock never ceases to surprise me. I am also surprised at the number of people who will leave the (well maintained and accessible) public right of way that goes through a section of my land in order to walk through fields, including ones with mares and their foals (or cows with calves at foot) "just for a change", then are surprised when the livestock aren't exactly friendly. I have locked gates to field which do not have rights of way running through them- you can climb the gate to walk through the field, but at least they gates can't be left open. I have even put signs up with warnings, but people seem happy to ignore them, yet moan when there are consequences to doing so. I know it's not everyone, but it happens often enough that I am fed up.
A good friend who is a farmer lost livestock not so long ago due to inconsiderate behaviour from walkers. This is his way of life and his business. How do you think the average business owner would take it if I walked into his office and trashed it, then said "well you got a good deal on the building and some other business people behave badly, so what are you complaining about?".
If you walk through a field with livestock, I am afraid you are taking a degree of risk (although in my experience sheep are more likely to be frightened of you than the other way round)- especially if they have calves/foals/lambs etc. Obviously, if it is a right of way then there should not be prohibited livestock there.