What would be out of place is the owner requiring the pilot to allow a child in the cockpit during flight.
Yes , this a tragedy. What is unforgivable is that it most likely was a preventable accident. This pilot failed in his duties as PIC. FAA will also investigate this "accident" and will find issues of non-compliance with regulations. In your comment you stated that it was not an error by the pilot. It most certainly was an error in judgement complicated by poor pilot technique.
If you only had the opportunity to view this "accident" personaly and witness what this pilot and his passengers suffered, including the life of an innocent 5 year old child, you might change your attitude about what you classify as to who or what to blame.
There's no "Jesus nut" on the EC135. Maybe you're thinking of the UH-1 series of helicopters.
Why would a "highly" experienced EC 135 pilot allow this?
The EC-135 accident helicopter was an EC-135T1 model. In December 2010 Europe issued an airworthyness directive on cracks in the hub on N,N1,G1, N2,N3,B ,B1 but no T1 models which the FAA implemented.
The NTSB always considers all global reports, airworthyness directives and historical accident reports but luckily not rumors, where this may have come from?
As a maintenance facility gets all relevant AD's it would have been prudent to for them implement checks on all similar models. Part of the NTSB investigation is the maintenance facility whiteness interviews and documentation so any flag that stood out there would marry with metallurgical component analysis of the "Jesus nut"