My golden snarls at a lady touching its head, abnormal?

Sometimes, my dog comes across someone he just doesn't like. I never know why, but he doesn't like them and doesn't want them touching him. If he doesn't do this again, I wouldn't worry about it. But if he does it again to another person, take him to the vet. Have a good look at his ears and around his head to see if he's hurt. He may be defending his head because it hurts. I'd let it go unless he does it again.