My take on the whole thing.
You build experience by making mistakes and learning from them. Those with low hours have not had the chance to make or learn from their mistakes and as a result have no experience on which to call on when things go wrong other than pulling out the book. General Aviation (in my opinion) tends to weed out those that simply can not do the job properly, which means those progessing from GA to the airlines generally know what they are doing. I say generally because I do accept some slip through the gaps.
The few low houred pilots I know who have gone to airlines have been less than steller pilots. One crashed a C206 on a low level go around simply because he did nothing with his feet, the plane yawed left and into some trees (bush strip). He could not find a job elsewhere in Africa after that but returned to Europe and is now sitting in the righthand seat of a 737. So here we have someone who lacked basic stick and rudder skills who now sits in the front of a plane carrying 180 passengers simply because he had the money to pay for a type rating.
Another example. Speaking with a Captain at a party once, he was telling me about a recent ILS approach into an airfield on a rather nasty day. He commented that in all his time sitting in the Left Hand seat, the only time he had EVER considered needing to take over from the FO was on this approach. The FO was simply overloaded and not coping. You couldn't really blame the FO though, he was a former Cadet with no real world experience and had never flown in wind like this before which leads me back to my first statement.
I have no doubt there are many great Cadets out there but I think my concern and the concern of many other pilots is that some not so great Cadets are also getting through. Even if (as some say) the experience gained in GA is not really relevant to today's airlines, I like the thought of the pilots up front (or beside me) having scared themselves a few times and learnt from it because that my friends, is one really gains experience.