Flying IFR is easy under normal circumstances IMHO. It is even easier for airline pilots - for example I flew from London to LA on a B747 recently and the amount of time spent in IMC was oooohhh....Nil.
That the flight might not have been in IMC doesn't mean that it is any easier.
Please do NOT confuse IMC with IFR. We've already had that discussion.
FLying some of the more complicated IFR approaches is pretty damn difficult, in VMC or IMC - it makes no difference. The tolerances remain the same, the possibility of misreading hte plate or the DME is the same, the possibility of busting an intermediate altitude is the same.
If you think being in IMC makes a difference, you know a grand total of ZIP about flying IFR.
Where there is a big difference for a relatively inexperienced private pilot is that, unless practising, he will be flying an approach for real, with few of the toys that Sick Squid has at his disposal, and the pressure will be on. He may be disorientated, worried and distracted by even a small equipment failure. Add in night and poor weather, slight traces of icing... We owe it to him to ensure he is trained to do it. If his training is less than that of an IR, then to higher minima.
Conversely, I accept that a daytime descent through a slight layer of stratus with base at 2000' AGL in +15 degC with a decent 3-axis autopilot switched into the HSI and a serviceable aircraft is not terribly taxing.
But there is little difference in conditions between those two scenarios that is allowable in a rating. One is not nice even for a professional pilot in good practice. The other is a doddle even for an 80-hour PPL.