I think we should keep this discussion in context.
Operating IMC carries a higher degree of risk than in VMC - period.
The types of IMC flying vary as widely as the conditions. There are a whole range of conditions that potentially increase the risk - icing, embedded CBs, heavy rain, turbulence etc.
IR pilots operate in the range of conditions (some wisley , some less so).
Broad statistics of CFIT accidents without knowing the conditions at the time, the experience and currency of the pilot etc tell us very little. It seems banal to comment that x% of CFIT accidents happen to IR pilots when in theory ALL CFIT accidents should involve instrument rated pilots because non instrument rated pilots should not be in those conditions anyway. I appreciate this is not the reality because non instrument rated pilots may inadvertently find themselves in these conditions. In that eveident the statistics do tell us they are unlikely to perform well.
So come on lets keeps things in proportion. Yes with an IR in the circumstances orginally outlined there may still be very good reasons for not transitioning into IMC - freezing conditions, CBs, rising terrain in the climb etc., and an IR pilot might be better of landing or continuing VFR. Thats an important part of his assessment and I dont think anyone has suggested that simply because the pilot has an IR he ignores other options.
However I still find nothing here to suggest that a curent IR pilot, subject to the aircraft systems working correctly and him not encountering freezing conditions, CBs, or rising terrain, will have many difficulties transitioning IMC and nor do I find any evidence (again subject to the caveats) that he would be safer scud running with rising terrain given the circumstances the orginal poster outlined.
DFC appears to suggest otherwise and I think he is wrong. I also think he is wrong becasue the "evidence" on which he relies does not support his arguement. It may well support other arguements - but not this one.