The most disheartening thing is that what you described is a good way to convince somebody, and even that often doesn't work. (As, I'm sure, many advocates of functional programming know well.)
If your goal is to convince somebody of something, this rational approach may be the best, in some sense, but it probably isn't the most efficient. Instead, I imagine a combination of some good points with a bunch of tactics borrowed from advertisers and behavioral psychologists is the most likely to actually convince people. I would love to believe that programmers are all rational and listen only to reason, but I've found this too often to not be the case.
Well, if you could absolutely convince anybody of anything, that would akin to hypnotism and will amount to fascism.
So, let's assume that you only want to convince people of things that are indeed true.
Then the thing goes awry: how do you know what's true? Maybe it's not, and they are rightfully not convinced. Maybe there are more than one ways that the thing can be seen. Etc.
Take something that is "obvious" for some people, like "PHP is a bad language".
It's not at all obvious to me that even that one universally true. One could answer, e.g: all languages have sore points so it's no big deal, if reversal of needle-and-haystack is your biggest worry about a library then it's pretty much fine, I can easily find programmers and that's what matters to me, it has never failed my projects, it works for Facebook, it has tools and communities I cannot find elsewhere like Wordpress, etc etc.
And PHP is as close-cut a case as it can get. Fighting Fortran? Not so much.
The most disheartening thing is that what you described is a good way to convince somebody, and even that often doesn't work. (As, I'm sure, many advocates of functional programming know well.)
If your goal is to convince somebody of something, this rational approach may be the best, in some sense, but it probably isn't the most efficient. Instead, I imagine a combination of some good points with a bunch of tactics borrowed from advertisers and behavioral psychologists is the most likely to actually convince people. I would love to believe that programmers are all rational and listen only to reason, but I've found this too often to not be the case.