It's slightly different. If Polanski didn't run from his crimes and spent a good chunk of his life working to help victims of sexual assault, I would be more inclinced to forgive him (he should still face justice, of course).
It's more than slightly.
1. The man in the other thread already served time as POW.
2. While genocide is a heinous crime and considerably worse than an individual or multiple rapes, but I do not consider the personality responsibility of a man cataloging confiscated items on the level of a man who raped (at least) a girl, even if the former was in service of a far more evil crime.
3. The man in the other thread has spent years atoning for his crime fighting against Holocaust deniers; Polanski has done nothing.
4. The man in the other thread willingly submitted himself to the justice of the court; Polanski fled.
I don't want to revisit all the debate of that thread, but I think there's more than enough difference here to see that one can defend one (that they still advocate some sort of sentencing for) while calling for the other to face a harsher punishment without some sort of cognitive dissonance behind their words.