People come with their egos in various sizes and shapes, some are down to earth, helpful to others and bring a smile to our faces. Some are the opposite, whom we would wish to avoid, I think your friend met someone who literally dampens the spirit of people around them. I don't blame him, may be he's hurt by this individual. What I do in such situations is, never to stoop down to the same level as them, then there would no difference between both. I would just have a exchanged a few pleasantries and move on. Now, let's think practically, your friend has certainly annoyed the principal by his indifference, the principal would certainly remember this and respond when he needs to approach her for a work or personal related favour or advise. I think we should grow up and move along having our own approach to others.