You can stop this one of three ways. First, if you have the Illusion perk Hypnotic Gaze, you can use Calm to pacify Grok just long enough to get away. Second, you can sheathe your weapon and yield to Grok. Finally you can steal the goat by sneaking up on the giant and talking with the goat in stealth. If nothing else, you can talk with the goat and then just start running.
Locations Found In
South of Rorikstead