Well, yes, they have the right to an opinion on criminal penalties, but gods forbid they should be allowed to exercise them.
Humans have a lot of problems. They tend to be swayed as much by emotion as fact, they almost never understand the entire situation, they follow the majority opinion, and they tend to count positive evidence (meaning pro guilty, in court cases) over negative (not guilty).
Psychologists say that it takes ten years of active practice to become a expert on a complex subject such as medicine or law. We leave the fate of any person accused to be decided by a jury consisting of laymen! A rational law-abiding citizen should consider passing judgment under these conditions to be immoral.
But that's just deciding if we should penalize the 'criminal'.
Our government is set up so that the actual law for which the criminals are being penalized for is decided by elected representatives. This means that, except for on controversial subjects like the death penalty, few criminal penalties are ever voted on by the voters. Those laws are decided by others... And those others are called special interest groups, i.e., the rich. Well, I don’t know if they’re any better than the masses, but I guess they must be doing something right…
If an average law-abiding citizen had the ability to punish that guy who was convicted of braking into his car and stealing his radio, the world would be a scary place... To the victim, any offence appears worthy of stern punishment. We may not be certain what will keep a person from stealing a second time, but it's not a fine -- and not a five year jail sentence either. Soon we would be dealing out death sentences for shoplifting.
We could let the majority vote decide for each type of crime, but then the laws would become even more stacked in favor of the majority. In many cases crimes that go against Christian values would be overpunished, while others would be underpunished. The laws would also be affected by what was in the news the month before. (The Columbine shooting put gun control in the schools as a priority for a while. In a year from now we may have almost forgotten it, and would vote differently, although the measures needed to prevent and correct these situations may be the same).
Long live the king!