The key difference is risk aversion.
Right, and there is risk in everything. A charity might fold, or end up consisting of crooks, or its cause might actually be harmful, or the estimate of buying malaria nets being more useful than supporting SI might turn out to be wrong. Hence the diversification.
Politics is even worse, you can never be sure which policy is better, and whether, when carried to its extreme, it turns out to be harmful.
This is where cousin_it's naive argument for radicalization falls flat.
Right, and there is risk in everything.
This doesn't matter. Whether you should be risk averse doesn't depend on how much risk there is, whether you should be risk averse depends on whether your pay-offs suffer diminishing returns, it is a mathematical equivalence (if your pay-offs have accelerating returns, you should be risk-seeking).
I think you don't understand risk aversion. Consider a simple toy problem, investment A has a 90% chance of doubling your money and a 10% chance of losing all of it, investment A has a 90% chance of multiplying your money ...
If it's worth saying, but not worth its own post, even in Discussion, it goes here.