The burden of proof lies with the trainers. Like my RW brethren before have stated, you won't last long in a helicopter if you do not make combined inputs. And big aircraft are aerodynamically not that different from light aircraft. If the FBW requires single input only, it was poorly designed.
Somehow I think this is a kneejerk reaction to the AF447 continued stall; I might be wrong though. But fly the damn plane and fly the simulator the same way. There are too many scenarios where you will have to combine inputs for this to work. Before you know it you will have someone sliding off a runway in crosswind conditions because he received negative training.
