Legalities of "right of way" do not exist in that context, EVERYONE has a right of way on public road. What you are referring to is Priority, and who should you give way to.
It is a requirement of the higheway code that ALL road users including pedestrians show consideration to others, Pedestrians should use the pavement where present, or, where none present, use the road walking towards oncoming traffic so as to be able to take avoiding action.
Now sure, the OP should be ready to avoid the person in the road, and he was, he is also within his rights to use his horn to notify said person of his presence if the person has not yet been alerted (ie he is walking on the wrong side of the road).
Now if the said person was using the blind side of a hill to CROSS the road, he has clearly not picked a safe place to cross, and again warrant s a reminder of his stupidity as at the end of the day, EVERYONE should regard everyone else as an idiot on the road, and no matter how much flesh he possesed it is gonna come off worse against a vehicle.
Final point, stopping and "bullying" the pedestrian (for that was what it seemed was intended) is far worse than any road crimes he may or may not have been guilty of.
Summation: OP tried to make out he was cool for calling out a pedestrian for giving him the v's and ended up looking like a male chicken.
OK, it sounds like I'm conflating priority and right of way, likely because of the fact that we refer to "giving way". Thanks for clarifying. I think my point still has some merit, semantics notwithstanding?