I would recommend "Why functional programming matters"[1] paper to anyone struggling to understand the purpose of functional programming. It's only about 20 pages.
That paper is a surefire way to scare people and keep functional programming from those that could use it perfectly well. You, and many others, vastly overestimate how capable even highly educated programmers are in understanding the arguments made in such a technical text.
[1] http://web.mst.edu/~tauritzd/courses/cs347/whyfp.pdf