Political theorist: Many people believe that the punishment of those who commit even the most heinous crimes should be mitigated to some extent if the crime was motivated by a sincere desire to achieve some larger good.
Conclusion (should)
Judges should never mitigate punishment on the basis of motives.
Evidence (since)
Even though some criminals with admirable motives do deserve mitigated punishments, motives are just a matter of conjecture so even vicious motives can easily be presented as altruistic.
Evaluate
The answers on Principle-Justify questions usually come in the form of "If Premise, then Conclusion", so an answer in that form would sound something like,
if motives are inherently speculative and even bad ones can be presented as altruistic, then judges should never mitigate on the basis of motives.
Sometimes the answers sound more like a "should-strengthener", so an answer in that form would sound something like,
judges should try to avoid mitigating punishment based on stuff that is essentially conjecture.
The most rare form of an answer only comes into play when the argument involves Weighing Tradeoffs, as this one does. When authors mention the pros and cons of doing X, if they conclude "we should do X", then we want an answer saying "the pro is more important than the con". If the author concludes "we shouldn't do X", then we want an answer saying, .
In this argument, the advantage of mitigating punishments based on motives is that some people with admirable motives would get the lessened punishment they deserve. The disadvantage is that people who had vicious motives could still present their motives as though they were altruistic, and so they might get a lessened punishment that they don't deserve. Thus, a Weighing Tradeoffs answer here might sound like,
It's more important that we don't let vicious people get undeserved lessening of their punishment than it is that admirable people get a deserved lessening of their punishment.
Goal
We know we need a principle that informs a judge how she should handle punishment / sentencing. Should she or shouldn't she be factoring in motives? We want our answer to help us say, "don't lessen the punishment based on motives".