You'll find another Port Righ on Skye (it's the island's capital). Spelled Portree nowadays.

As an Ayrshire man I've always assumed the Kintyre/ Carradale Port Righ was linked to Robert the Bruce. He was very well known in those parts and stayed at King's Caves (a few miles across the Kilbrannan Sound from Carradale's Port Righ) on Arran's West Coast for some time during his guerrilla war years between 1306 and the triumph of Bannockburn in 1314. The hills directly above the King's Caves on Arran are called Torr Righ Mohr (The Big Hill of the King) and Torr Righ Beag (The Small Hill of the KIng). Bruce also had land - and a stonking biffer of a castle - on the Ayrshire Coast at Turnberry.