This is a common debate that people like to bring up that makes me laugh more and more as my experience increases.
Most new riders will have a crash. However, most of those crashes are not related at all to the displacement of their machine... this is just one of those topics that is 'en vogue' to bring up and more experienced riders like to talk about in a somewhat condescending fashion. I'll admit, I've spoken like that to people considering getting into riding.
The scenario is more that some people have the skills to start riding and do well right off the bat, some will do alright but have some trouble along the way, and some will never be good riders. That's just the way the cookie crumbles.
The bottom line is that it really is all dependent on the person. But, since new riders often come looking for advice and they are not yet known by the experienced riders giving said advice, I will admit that suggesting a slower/older/used bike is probably a good idea.
However, writing a 10 page diatribe about the intricacies of technique and why a ninja500 is the only option for a new rider is laughable at best.
By the way, I started riding a year and a half ago on my first bike, a brand new 06 r6. I think I've done alright...