"They should have been digging ditches in Africa or volunteering at their local soup kitchen or whatever."

No, what they should have done is written their books, then donated a large fraction of the money they earned from writing them. If you're that good of an author (keeping in mind that 99.99% of people aren't), you can help the world a lot more that way than by volunteering at soup kitchens.

"It's a good thing not everything felt as you did or the world would be pretty bleak indeed."

If everyone felt as Eliezer did- that it was better to spend at least some effort doing what the world needed most, rather than what happened to feel good- then maybe we would not have hundreds of millions of people in constant danger of starvation.