I'm of two minds. Tax fraud is a fairly common crime among the wealthy. Tim Geithner admitted to tax evasion over a period of several years during his confirmation hearings, then went on to serve for four years as Treasury Secretary.
The rage--and rarely have I seen such rage in politics--against Cahuzac seems to stem from two separate sources: that he brazenly lied (we are asked to believe) to the "highest authorities of the state" (the president, the prime minister, and the National Assembly) and that he was supposed to represent "rigor" in an age of austerity, clawing back money from widows and orphans after feathering his own nest quite lavishly over a period of 20 years.
The troubling thing is that Cahuzac's effrontery reinforces the "tous pourris" thesis of the extreme right and the universal fecklessness ("qu'ils s'en aillent tous") thesis of the extreme left. He completes the disintegration of the Strauss-Kahnian wing of the party and accredits the idea that la gauche caviar has cloaked a reign of plunder in a rhetoric of social justice.
For some, Cahuzac is just another corrupt politician, subject to "the thousand natural shocks that flesh is heir to." For others, he is a symbol of some profound failure of the French state and the elites that sustain it. Should one grant absolution to the political class or acknowledge that the time for deep reformation has arrived? Normally, I believe that moralistic politics makes for bad politics, but something about the baldfaced impudence of Cahuzac arouses the latent moralist in me and makes we want to shed tears along with Gérard Filoche, who regrets what a Socialist government might have done in France and probably will now never do, as it forfeits its last shred of credibility.