Firstly pilots need to be aware of their own limitations and that of the aircraft also. Flying IMC without holding IR (was the a/c IFR equipped?) is dangerous business, just look at the statistics.
And yes it is a CRM issue. If you have two qualified pilots in the heli then you should work together in difficult times even if you are not flying dual crew. The PPL pilot should respect the inexperienced CPL views and take note. Dont become another statistic!