Steve - life is far too short to even try to do so. If someone says/shouts something which isn't 'true' just wave and shout a cheery 'good morning' or 'have a good ride' (or whatever). I think we can all agree that it would be nice to be able to ride on cyclepaths without the aggravations (surface, debris, obstructions, 'Give Ways', design wiggles, other users
) but we live, in UK anyway, in the real world. And a cyclist who takes on the load of 'explaining the law' to others is on an infinite road (
) to personal frustration. I'm with
@Drago here: have a 'ready to deliver' positive greeting in your response quiver, and ride on, on path or road "in a way that is considerate to the comfort and safety of others".