You could argue that some feelings do change things and have an effect on actions; sometimes in a negative direction (i.e. anger leading to vengeance and war) sometimes in a positive direction (i.e. Gratitude resulting in kindness and help.) Anger in this example can be considered "pointless" not because it has no effect upon the world, but because it's effect is negative and not endorsed intellectually. I think that's the sense in which despair is pointless in the original example. It does have an effect on the world; it results in people NOT taking actions to make things better.

You could argue with the use of the word "pointless", I suppose.