French Culture Minister Frederic Mitterrand was quoted in French media as saying, "In the same way that there is a generous America that we like, there is also a scary America that has just shown its face."
The law is supposed to be scary to criminals -- and the law's persistence, over the span of decades, is scarier still, but rightly so. People shouldn't be able to evade justice by fleeing to a hospitable jurisdiction. Sometimes they in fact can, because of various legal restraints on extradition. But if they slip up and fall outside the protection of those regimes, justice should indeed pursue them, and in the process scare others into realizing that justice is not easy to avoid.
Conversely, generosity here would be a misplaced generosity. The only person who rightly deserves generosity is the victim, who understandably doesn't want a fresh outbreak of publicity. Some victims are emotionally helped by the punishment of those who victimize them, but others might on balance be hurt by it. And indeed this risk is usually greater many decades later, when the satisfaction of knowing that the person who harmed you is being punished is generally less, and the worry about renewed unwanted publicity is the same or even greater.
But we also need to think about not just generosity but also the simple debt we owe to other potential victims, to do what we can to prevent such crimes in the future -- both by deterring potential victimizers and by reinforcing the norm that even fame, money, and talent shouldn't protect one against punishment. And generosity to Polanski? It's hard to see why he is a fitting target for generosity. Some say he has suffered enough; and without doubt he has paid a cost. Practical exile even to a friendly country in which one can still work and be celebrated is something of a cost. But it's not the sort of cost, it seems to me, that criminals of this sort need to pay.
Naturally, much depends on the nature of the crime. The milder the crime, the less of an imperative there is for punishment, and of course the less the proper punishment should generally be. And even this crime, while serious, is not as horrific as some crimes, such as murder or forcible rape of children. (The statement of the victim, to the extent that it is uncolored by the financial settlement with the criminal -- and I can't say in this case whether it is or it's not -- is certainly some evidence of the magnitude of the harm done in this case, which in turn is part of the evaluation of the magnitude of the crime.)
But this was no normal tryst with a 17-year-old, of the sort that might be labeled statutory rape but is generally not prosecuted, may not be much different from legal sex with an 18-year-old, and would in fact be legal throughout most of the United States. This was apparently sex with a 13-year-old girl to whom Polanski had given champagne and part of a Quaalude. By any standard, this is a very serious harm, one for which the "42 days in prison [spent for] diagnostic tests" before the conviction does not seem an adequate punishment, especially given that Polanski's fleeing lost him the benefit of any sentencing discount he might have hoped to get for plea-bargaining (though it sounds like the discount wouldn't have been as much as he'd wanted).
So, yes, it's a scary part of America that tries to pursue justice even 32 years later. And there should be a scary part of France that does the same to those who commit serious crimes in France, and a similarly scary part of all civilized countries.