This chap is like an OAP clarkson, making amusing generalisations and blaming anyone but himself.Erosion is a fact of life wherever man goes, walkers horses bikes vehicles all contribute, there are plenty of paths that never see a bike and need repair just from footfall.
The walkers I have encountered are largely good natured, usually impressed that you are biking in the hills, I think provided you're not frightening them with excessive speed they are mostly fine. The only walkers with bad attitudes I have ever encountered seem to be the over 60's ramblers in larger groups, who have grown old not been used to, or accepting of bikes on their beloved walks.