The lawyer’s argument isn’t concerned with deterring or otherwise preventing crime, just with the unfairness in requiring nonviolent criminals to pay for the consequences of violent crime. Because this principle is all about deterrence, it can't get us to a conclusion about fairness.

The lawyer doesn't actually discuss how severe the overall penalties for different crimes should be; the argument is much more limited than that. The lawyer's point is that it's unfair to make nonviolent criminals specifically pay a surcharge to support violent crime victims.

Whether nonviolent criminals have to pay this surcharge isn't related to the overall severity of their punishment—if a nonviolent criminal gets a 10-year prison sentence but no surcharge, as far as we know the lawyer would have no issue with that. (B) is incorrect not because it's too strong, but because it relates to a different issue than the argument: severity of punishment as a whole rather than the fairness of this specific surcharge.

This principle has nothing to do with the fairness of levying the surcharge on nonviolent criminals, meaning it can't bridge to the correct conclusion. Besides which, there’s no indication that the money is going to anything other than services for victims—so this principle doesn't trigger either..

The support says that petty criminals must now pay for services for victims of violent (i.e. more serious) crimes. That triggers this principle, which tells us that nonviolent criminals should not be forced to pay for such services. In other words, it's unfair to do so—which is exactly the lawyer's conclusion, meaning this principle effectively bridges the gap.

The argument doesn't mention how the value of any stolen property compares to the surcharge, nor does it discuss what a better fine amount would be. The lawyer is saying that levying a surcharge on nonviolent criminals in support of victims of violent crimes is unfair, and this principle doesn't get us closer to that conclusion.