It's a useful exercise for aspiring economists and rationalists to dissect charity into separate components of warm fuzzies vs. efficiency. However, maybe it's best for the general population not to be fully conscious that these are separate components, since the spirit of giving is like a frog: you can dissect it, but it dies in the process (adaptation of an E.B. White quote).

Lemma: we want charity to be enjoyable, so that more people are motivated to do it. (Analogy: capitalist countries let rich people keep their riches, to create an incentive for economic growth, even though it might create more utility in the short term to tax rich people very highly.)

Consider this quote from the article:

If he went to the beach because he wanted the sunlight and the fresh air and the warm feeling of personally contributing to something, that's fine. If he actually wanted to help people by beautifying the beach, he's chosen an objectively wrong way to go about it.

Sure, but making the lawyer conscious of this will give him a complete buzzkill. He will realize that he was unconsciously doing the act for selfish (and kind of silly) reasons. Your hope in telling him this is that he will instead opt to use his $1000 salary to hire people, but I question whether he would actually follow through with that kind of giving in the long run, since his unconscious original motive was warm fuzzies, not efficiency. In effect, you may have prevented him from doing anything charitable at all. Don't let the perfect be the enemy of the good.

So, this article is great fodder for someone trained in rationalist/economic thought, but keep in mind that this type of thinking makes many people uneasy.