One is reminded of the joke in the book The Little Prince
where the businessman explains buys and sells planets and
is asked by the Little Prince why. To make money, he replies!
And what do you want money for asks the Little Prince. The
man replies that by having more money, he'd be able to buy
more planets, of course!

We may "invest to make money, not to save the world" as you say,
but why do we want to make money in the first place? Money
is a means to an end, not an end.

However you define your "ends" it boils down to living well with satisfaction and fulfillment and being at peace with the world around you. It's hard to believe that a (non pathological) person
could ever fully obtain those things if they were fully aware of their close aiding and abetting of things they felt were morally repugnant.

So once you know what you personally classify as morally
repugnant (in this case murderous behavior towards African
children, being the example you provided) then defining
the spectrum from "distant almost impossible to avoid involvement"
to "directly aiding and abetting" is how most folks would probably
end up deciding when they are comfortable investing and when not..

What's sad to me is that we even need to have some of these
discussions (I speak of society and no single poster here)
as it used to be just obvious some decades ago but in recent
decades, probably since the 80s it has been "uncool" to
actually (gasp!) care about the wellbeing of fellow human
beings more than about money...caring about other
human beings more than about money is among the most basic "moral
values" issues I can think of (as well as being a traditional
religious principle) yet those who scream about moral values
and traditional and religious values have (among them) more
than a few who participate in the demeaning of anyone
who actually expresses caring for fellow human beings (or the
planet or...) above money and the profits of corporations.

Corporations were created to serve humankind, and we have
forgotten that to the point that we seem to believe that
humakind was created to serve corporations..and that
is our great confusion. Same with profits, same with money.
When money is used to serve humanity, it is not the
root of all evil. When humanity is serving money on the
other hand...