As the son of one American immigrant and the father of another, I find it hard to muster much empathy for Facebook co-founder Eduardo Saverin and his decision to renounce his US citizenship.

Saverin, who was born in Brazil and brought to this country as a child, turned in his American passport last year and moved to Singapore; it is widely assumed that he did so to reduce the taxes he would otherwise have to pay on the billion-dollar gains generated by Facebook’s IPO. Saverin denies, not very convincingly, that his expatriation was motivated by tax considerations. “His decision had nothing to do with dissatisfaction here,” a spokesman said, “but with his strong desire to do business there.”

Well, it takes all kinds to make a global economy, and maybe Saverin genuinely prefers doing business in a quasi-authoritarian society where freedom of the press is unknown. Singapore’s economy is one of the world’s freest, and its taxes are considerably lower than America’s. If such things matter more to Saverin than the blessings that come with American citizenship, it was always his right to leave. At least he had the grace to describe himself as “very grateful to the US for everything it has given me.”

Yet while Saverin may not come across as the most appetizing of creatures, he is not nearly as odious as US Senators Chuck Schumer of New York and Bob Casey of Pennsylvania. To hear the two Democrats tell it, Saverin is a virtual traitor, a turncoat who has sinned against America and must be given no quarter.

“It’s infuriating to see someone sell out” – sell out! – “the country that welcomed him and kept him safe, educated him and helped him become a billionaire,” Schumer snarls. “We plan to put a stop to this tax avoidance scheme. There should be no financial gain from renouncing your country.” Casey inveighs against “allow[ing] the ultra-wealthy to write their own rules” – Saverin’s departure, he says, is “an insult to middle class Americans and we will not accept it.” The senators have introduced legislation that would penalize wealthy expatriates by imposing a 30 percent capital gains tax (double the current rate) on all their future US investments, and bar them from ever re-entering the United States.

Even by the usual standards of congressional demagoguery, this is appalling. Saverin broke no laws. He didn’t cheat on his taxes. He certainly didn’t write his own rules. In fact, under existing law expatriation vastly enlarged his current tax bill, by deeming most of his investment gains to have been realized and taxable on the date he renounced his citizenship. Far from escaping the taxman, Saverin’s Facebook fortune enriched the US Treasury by hundreds of millions of dollars. It is only gains he accumulates after giving up his citizenship that will avoid the reach of the IRS.

But if Schumer and Casey really believe that citizens who pick up and move to improve their tax status should be smeared as sellouts and punished ex post facto, why stop with Saverin? Every year, millions of Americans relocate from high-tax jurisdictions to those with lower taxes. Between 2000 and 2010, for example, Schumer’s state of New York, which has one of the nation’s heaviest personal tax burdens, experienced a net outflow of 1.3 million citizens. Hundreds of thousands of those ex-New Yorkers now reside in Florida. Many no doubt moved for the weather, remarks Scott Hodge of the Tax Foundation, but how many more preferred the sunnier tax climate in Florida, where there is no individual income tax, no estate tax, and no inheritance tax?

When former Cleveland Cavalier LeBron James, spurning an offer from the New York Knicks, joined the Miami Heat two years ago, it was noted that he had a clear financial incentive to do so: Income taxes in New York would have cost him more than $12 million. Would Schumer call him a “sellout” too? Leaving Cleveland’s high taxes behind saved James millions as well. Should Ohio lawmakers pass a law banning him from ever setting foot in the Buckeye State again?

Casey and Schumer both maintain Facebook pages, which together have been “liked” by more than 17,300 people. Thanks to Facebook, their reach is extended and their message amplified – all at no cost to them. They benefit every day from Saverin’s willingness to do something they never did: invest his savings in a risky start-up venture with no guarantee of success. Rather than slamming him for leaving the country, perhaps they ought to be thanking him for what he helped make possible. Or better yet, repairing the US tax code so it doesn’t drive people like Saverin to seek economic refuge elsewhere.

Saverin may not be very lovable, but he at least understands economic incentives. Schumer and Casey, by contrast, have yet to grasp that the more governments try to soak their taxpayers, the more likely those taxpayers are to end up somewhere else.

(Jeff Jacoby is a columnist for The Boston Globe. His website is www.JeffJacoby.com).