The practice of hiring immigrants is often portrayed as a moral failure that threatens America’s citizen labor force. That is certainly Donald Trump’s stance in his presidential campaign. The Republican candidate has called Mexican immigrants rapists and has promised to build a wall on the Mexican border. He has even pledged to reduce the number of and increase the burden on legal immigrants. According to Trump, immigrants are bad. Hiring immigrants, therefore, is also bad.

In his own employment practices, however, Trump’s stance on employing immigrants is more nebulous. This week, several former models employed by Trump’s modeling agency, all immigrants, said they worked for the real estate magnate without a proper visa. Some even alleged that they were encouraged to evade immigration and falsify customs forms.

Even closer to home, Politico reports that Melania Trump herself may have violated the terms of her visa when she was working as a model in the mid-1990s. Mrs. Trump says that she had to return home to renew her visa every few months, which suggests she held a tourist visa. It’s unclear whether she was paid for the modeling she did in 1995, but if she was, it’s likely she was not in compliance with immigration law. The Trumps responded by saying that Melania would address the issue in a press conference, but she has yet to do so.

Afterward, Kevin D. Williamson at National Review Online called for the deportation of Melania, even though she is now a U.S. citizen, having married Donald. Williamson isn’t especially concerned with the legal ramifications of stripping someone of citizenship; he just argues that, given Trump’s anti-immigration stance, it would be fair to kick Melania out of the country.

Rather than use Trump’s failings as an excuse for more immigrant bashing, José Jorge Mendoza, an assistant professor of philosophy at the University of Massachusetts, is arguing for a different path. According to Mendoza, the key takeaway about Melania’s immigration status is not that she’s a criminal who deserves to be punished, but rather that she highlights the complexity of the system—and the failure of Trump’s understanding of it.

Mendoza has a personal stake in this conversation; his family includes immigrants, giving him a strong understanding of those laws. “My mom and my aunt would come in early Monday morning and work Monday through Friday cleaning houses, living with their employers. Friday night they would go back and spend the weekend with their families in Tijuana, which was a common thing for a lot of undocumented workers to do,” he says. “Their entrance and exit is completely lawful, but they’re actually working, which is not part of their technical visas.”

Judging Trump as morally wrong for hiring immigrants makes it easier for Trump himself to abuse that community.

The fact that tourist visas are used in this manner emphasizes one of the largest problems with Trump’s proposed wall. “You’re not solving the underlying issue,” Mendoza says. “You can have the biggest wall in the world but there are people who will still get in with tourist visas.” Melania Trump was in the United States legally, just like any other tourist visiting the United States legally. Even if you could, you wouldn’t want to prevent all passage back and forth across the border. The U.S. issued 10.8 million nonimmigrant visas in 2015; nullifying those visas would have a massive effect on the economy. As long as people cross the border, some of them are going to work. As Mendoza says, “This idea that you can isolate the economy from the rest of the world is dubious.“

Some jobs, Mendoza points out, are restricted for safety reasons; you need a special license to drive a tractor-trailer. Other jobs are understandably restricted for ethical reasons, such as bookmaking. But why should all jobs be restricted because of your country of origin? Mendoza argues that there’s no compelling moral case for it. Melania didn’t do something wrong by working, nor did the immigrant-models employed by Trump Model Management. Rather, immigration opponents like Donald Trump threaten the U.S. labor system by stigmatizing those who have been born in the wrong place.

The models at Trump’s agency allege that he deliberately exploited them; they had to live in cramped quarters and if they did not obtain work visas, they had rent and fees subtracted from their earnings. This is a pattern for Trump; when he was building Trump Tower, he supposedly used undocumented Polish immigrants for demolition work. In some cases, workers were never paid, nor were they provided with protective helmets or eyewear.

Undocumented workers, or immigrants working semi-legally because they hold the wrong kind of paperwork, are easier to intimidate, mistreat and exploit. Calling for Melania’s deportation or judging Trump as morally wrong for hiring immigrants makes it easier for Trump himself, and his supporters, to further stigmatize and abuse that community. Even if Melania and a handful of models violated the terms of their visas, they didn’t do anything morally wrong—unlike Trump, who promotes and profits off of hate.