Hassled, I think 8 yrs old is a good age to think and talk about these things. We did a project with our Brownies (and all Brownies/Guides and Rainbows across the country will have been involved to some extent) called 'Changing the World', and the girls were very enthusiastic about the ways in which they could help, and the results, although small in the general scheme of things, were impressive.
I understand you don't want him to dwell on it as a hopeless case that would upset him, but I think engaging in a positive way about inequality, and about how we can all fo a little bit to help, is a good thing.
I do agree with MdmeBody though that it was a bit of a sweeping generalisation re pampered rich kids in the west etc. Although in other ways it is all relative. Whilst there no is no denying that children live in poverty here and in the US, there are relatively few children in either country who don't have access to safe drinking water, education, and a roof (of some kind) over their heads. Not saying this means they're all fine and dandy, of course they're not, but not having those things is also the reality for kids in lots of countries, so I think context is important too.
D