How do you suggest your over 40 family man genius programmer could be identified as a genius programmer by someone who does not know him?

As a recruiter you may not like this answer, but you'd have to ask him questions that require him to demonstrate ability rather than interest. You may not like that because it requires you to possess a lot of the skills the jobs you are looking to fill require, and there's not a shortcut to that. In my experience recruiters tend to be heavy on buzz words but light on actual understanding of programming itself. In an earlier response you made a statement that suggested that because you're in recruiting you don't need to have the same passion as a programmer would. If passion does in fact determine interest and ability, then you really should be studying programming outside working hours, as it will only help you as a tech recruiter to better understand the skills required to program.

There's nothing wrong with asking somebody about what they do outside work in and of itself, but its just a single data point and certainly not the most important one. I've interviewed and hired many, many programmers and my typical routine is to look at their resume to get a baseline of what their experience is. I have never, not once, looked for a specific language or framework. The reason is that experience tells me that if somebody is a great C++ programmer, they will be a great Java developer, a great Ruby developer, and so on. If they claim to have experience in C++, I may ask C++ specific questions, but I'm really only interested in knowing whether they really have an expert level understanding of object oriented programming principles and use good design practices. On the other hand if somebody has a cursory amount of experience in ten different frameworks but are only mediocre in each, they will be mediocre at every task until they gain a deep understanding of the fundamentals.

And let me make a point that I have tried to make when I participate in these discussions - what EXACTLY is a "great developer"? In hard, definable, quantifiable terms?

That's like asking "what makes a great auto mechanic?" It's some combination of experience and a fundamental understanding of the inner-workings of an automobile. Hearing a strange noise coming from the engine on your car? Drawing on his experience, a great mechanic can better diagnose and fix it than a bad one. Is there a score to measure that skill? No. You'd have to be an experienced mechanic yourself and observe a mechanic working in order to make that determination. It's not quantifiable. If it were, you'd be out of a job.

I don't know anything about your experience, so I'll certainly not make assumptions about you specifically, but in my experience most recruiters don't have any experience at all in programming. They haven't built a single Rails app, made a commit on Github, and couldn't explain what object relational mapping is. What a curious thing then that they are attempting to measure a person's ability in those skills. That's why developers tend to resent recruiters. They spam people indiscriminately and often clearly demonstrate that they have no understanding of what they are asking. This shows a lack of respect for people's time. David Heinemeier Hansson, the inventor of Ruby on Rails, has famously tweeted on several occasions solicitations from recruiters asking for more years of experience in Ruby on Rails than the language has existed.