It's hard to convince someone that their solution to a problem doesn't work, until it doesn't work.
We cling to our idea. Our experience clarifies our expectations.
When I'm trying to influence someone to consider the ramifications of their ideas, I've learned to first validate the idea (identify whatever is useful about it or appealing) before guiding them thru any analysis of the idea. Seeing the truth can be tough enough, without adding emotional resistance to the mix.
It's easier for someone to convince themselves. Convincing them is hard. Let them convince themselves.
-- doug smith