I have certainly never gone out with the intention of causing an actual face to face confrontation, and I would wonder at the motivation of anyone that did. On a handful of occasions over very many years of walking I have unfortunately had it forced on me. That is not to say I haven't tried to calm the situation but when confronted by unreasonable and frankly illegal behaviour I have stood my ground and pointed out that I do know what I'm talking about. Statistically it's probably not going to happen to many people and surely no one wants a good walk spoilt by it
That extreme form of "landrage" is thankfully extremely rare in my experience; but "landrage" must not just be thought of in the context of actual confrontation with a landowner or other. It takes many forms and this is what I believe BWW is referring to. For example: not reinstating rights of way, blocking/obstructing ROW, excessive private property/keep out signage, misleading signage to confuse and deter, and damaging/destroying official signage. All of these when consciously done by a landowner are symptomatic of "landrage".
The question is of course why do some landowners suffer from the condition? Perhaps it is borne of a sense of insecurity and the often quoted fear of crime. But how often have you as a walker or have you seen another walker committing criminal damage for example? The yobs with anti social intent will make no distinction between ROW or not. Do hare coursers or poachers only use ROW to commit their crimes? Obviously not so why should some landowners view walkers on a par with others intent on criminal behaviour. It doesn't work in my mind as a valid argument against reasonable access. I discussed this issue with a landowner once (not a confrontation just a friendly chat) and when he came out with this fear I pointed out that he should be encouraging more law abiding walkers onto his land. More eyes on the lookout for the dodgy characters and less likely that they would try something with more people around. The landowner conceded that I did have a valid point
There are so many other examples of "landrage" and of course many other theories that can be explored, but I would say to those that think they haven't experienced it that they probably have but just haven't realised what it was