I have some thoughts on the man from whom you suffered a sling tonight, but first here's a charming anecdote:
When I was 11, I moved to a new school district. I moved a lot, and I never changed, only the mass mindset of each new class was different. Anyway, at this school the other seventh graders decided I was ugly, and always let me know it. Of course I wasn't ugly in the least, but that's not the point. I realize now that they were simply children at that horrible cusp of puberty, but I know the feeling of just sitting alone reading a book and suddenly being insulted. I eventually moved away, and have never been called "ugly" again. Now before this experience, I would laugh at an obese person or smirk at anyone wearing odd clothing. But after my seventh grade year, I never insulted anyone in that way again, as a joke or in anger.
I think the difference is maturity and experience--that man has probably always been "popular", to use a high school term, and just hasn't had the real human experience. The godawful insecurity that is adolescence can excuse my tormentors, but yours...just a fluke, a person who has had no depth to his life, and is to be pitied. I'm sorry about your grandfather.