A few days before the Super Bowl, MSNBC embarrassed itself with an obnoxious tweet implying that “rightwing” conservatives are such bigots that they were bound to “hate” a Cheerios commercial featuring a biracial couple and their adorable daughter, Gracie. The backlash was blistering and instantaneous, and the cable channel apologized and deleted the tweet.

When it comes to playing the race card against anyone to its right, MSNBC is a recidivist. The smear over the Cheerios ad came just a few weeks after an on-air panel smirkingly joked about Mitt and Ann Romney’s newly-adopted black grandson and how incongruous he appeared in the family’s Christmas photo. That flap also triggered an uproar, followed by multiple apologies.

Count me among those who can’t imagine anyone this side of the fever swamps viewing that sweet Cheerios ad or the Romneys’ quiver full of grandchildren with any kind of racial disapproval, let alone one driven by politics. That some on the left can so casually traffic in such slander reflects nothing but their own bigotry against conservatives.

If you asked me, I’d have said that was self-evident. (As a right-winger with kids of different colors, I may be biased.) But Jim Lindgren, a law professor and sociologist at Northwestern University, decided to double-check. He turned to the General Social Survey, a comprehensive national survey that for years has been compiling sociodemographic statistics on US residents – including (among many variables) data on respondents’ political leanings and the racial makeup of their families.

Not surprisingly, Lindgren found, there was nothing in the data to back up MSNBC’s suggestion that conservatives are more likely than liberals to frown on biracial families.

“Among families with step-children or adopted children,” he wrote for The Volokh Conspiracy, a legal blog hosted by The Washington Post, “11 percent of conservatives were living in mixed-race households compared to 10 percent of liberals.” Broadening the analysis to include families with biological children of an interracial couple (like Gracie in the Cheerios spot), Lindgren found that 11.9 percent of self-identified conservatives live in mixed-race families compared to 11.4 percent of liberals. When the numbers were sorted by party affiliation, they showed 9.5 percent of Republicans living in mixed-race families vs. 11.2 percent of Democrats. Crunching the stats by both race and ideology, 2.0 percent of white conservatives live in mixed-race families, while 2.4 percent of white liberals do.

None of these differences are statistically significant. Taken together, they reinforce the ugliness of MSNBC’s taunting insinuation that to be politically right-of-center is to be racially intolerant, or that there is something inherently liberal in forging ties of love across the color line.

But there is also a message here that conservatives and Republicans should be taking to heart, one that has nothing to do with liberal closed-mindedness.

In the ongoing debate over immigration reform, there are reasonable arguments on all sides – arguments about the economic, social, and environmental impact of increasing the number of immigrants, sealing the US-Mexican border, or offering amnesty to illegal immigrants. What is not a reasonable argument, it seems to me, is the claim that more immigrants must mean fewer Republicans.

“At the current accelerated rate of immigration – 1.1 million new immigrants every year – Republicans will be a fringe party in about a decade,” writes Ann Coulter in a recent column. She cites a wide swath of polling data showing that most immigrants not only come from “societies that are far more left-wing than our own,” but that “they bring their cultures with them.” Hispanic and Asian immigrants may have little in common economically or culturally, but “both overwhelmingly support big government, ObamaCare, affirmative action, and gun control. … How are Republicans going to square that circle?”

But that kind of essentialist argument is as flawed as the claim that interracial families must be left-wing, or that a conservative message of liberty, opportunity, and patriotism can only appeal to voters with white skin.

For more than half a century after the Civil War, blacks were a solid Republican constituency, and the most Democratic-leaning states were the most hostile to black voting rights. Yet attitudes change – sometimes for good reasons, sometimes not – and voting patterns with them. Political values aren’t coded in our DNA. Party loyalty isn’t a function of immigration status.

Where do you stand on amnesty? Whom you support for president? Would you ever watch MSNBC? If you’re looking for the answers in the color of your skin, you’re definitely doing it wrong.

(Jeff Jacoby is a columnist for The Boston Globe).