What I find embarrassing about knowing just a little bit about a subject is that outside of a formal class, there are few places to talk about it; particularly, few places to talk about it with people who will bring your further toward understanding what you've learned. If you learn a little bit of the mathematics of a subject, you're not interesting to the specialists, and most others won't be interested in the subject at all.
It seems easier to find a community around learning things that are less academic subjects, where you'll generally learn them in an informal structure anyhow -- cooking, crafts, foreign languages.
(I do like the idea of The Simple Math of Everything...)
The dust specks seem like the "obvious" answer to me, but how large the tiny harm must be to cross the line where the unthinkably huge number of them outweighs a single tremendous one isn't something I could easily say, when clearly I don't think simply calculating the total amount of harm caused is the right measure.
I had a friend in college who was a philosophy major; he'd been raised a fundamentalist Christian, and turned from that into some sort of chaotic evil deist. I used to enjoy arguing philosophy and ethics with him. But the further he got into his study, the more his arguments turned into half-understood quotations of Wittgenstein and Kant, and his debating technique turned into sophistries and trying to name and call out others' logical fallacies, sometimes correctly and sometimes not -- the same techniques he grew up with, only without having to wake up early on Sunday. I don't argue with him anymore...