gums,
Comparing the Viper and the Airbii is possible (they both fly) but one must take care.
If I undertood you correctly, you're not happy because of the multiple potential levels of degradation of the FBW in the airliner. And you base your PoV on the much simpler (in term of number of possibilities) of the Viper.
Let's not forget that the Viper cannot be flown without FBW computation (i.e. no Direct law, nor mechanical reversion), due to its instable nature. But the pilot can eject.
On the other hand, one doesn't eject from an airliner. But in the same time the airliner is stable, hence it can be flown without FBW computation (i.e. Direct law in pitch or in mechanical reversion).