From the perspective of a certain kind of person, helping the poor has a strong appeal in that it's a way to feel like a good person. To put in a big effort that is appealing--children playing, women saved from work, water for free--is a victory, even if it was obviously doomed to failure from the start, because you have demonstrated to others, and to yourself, that you are a Good Person who cares about these things. Once you realize charity is more about this instinct than producing maximal good, the irrational charitable actions of others begin to seem more rational.

Not every person is this way but it's easy to see how these bad ideas can take root once they have a critical mass of appeal and influence in an in-group. Many do-gooders--many people in general--have really never got the tools to think about physical or economic considerations, and can't distinguish between a correct naysayer and an incorrect one. So, under the influence of a highly appealing idea, even things that should seem obvious (like the laws of physical mechanics, or local socioeconomic considerations) are hard to distinguish as correct or incorrect. Critically, they are an obstacle to being a Good Person, and therefore probably wrong.