Carb ice is most likely to form in certain conditions as you well know. Flying in those conditions conducive to it, is the time for it to be applied, actually before entering those conditions would be better to allow for the warm up time. Avoid reduced engine power. During training and during the theory exams, you will learn all about it and can't use the defence you never knew about it.
If the carb icing system is defective thats a different matter.
I'm not surprised at all by the legal stand being taken, as the USA is such a litigious society nowadays.
ie lets sue Macdonalds because I got burned by spilling their coffe onto myself. (or lets sue them because my coffe was cold?)
