The Houston Chronicle said the truck's owners have no plans to remove the custom graphic, which they ordered after Trump's election.
"It's not to cause hate or animosity," Karen Fonseca told the Chronicle. "It's just our freedom of speech and we're exercising it."
The Chronicle reported:
"Fonseca said the truck belongs to her husband but that she often drives it. They had the sticker made and added it to the window after the billionaire real estate magnate and reality TV star was sworn into office.
"The sticker has attracted attention many times before, Fonseca said. People shake their head. They take photos of it. Officers have pulled her over but failed to find a reason for writing a ticket.
"It makes people happy. They smile. They stop you," Fonseca told ABC affiliate KTRK.
"They want to shake your hand."
The Texas chapter of the American Civil Liberties Union offered to help Fonseca - and provided Nehls with a "Constitutional Law 101″ lesson: "You can't ban speech just because it has [expletive] in it."
Texas penal code describes disorderly conduct as "intentionally or knowingly [using] abusive, indecent, profane, or vulgar language in a public place, and the language by its very utterance tends to incite an immediate breach of peace." Making "an offensive gesture or display in a public place" is also prohibited if "the gesture or display tends to incite an immediate breach of peace".
But the ACLU cited a 1971 Supreme Court decision, Cohen v California, in which the high court overturned a man's disturbing-the-peace conviction after he'd gone to a courthouse in Los Angeles wearing a jacket that said "(Expletive) the Draft."
At a news conference on Wednesday, after his Facebook post went viral, Nehls said he supports freedom of speech, according to the Associated Press.
"We have not threatened anybody with arrest; we have not written any citations," Nehls said.
"But I think now it would be a good time to have meaningful dialogue with that person and express the concerns out there regarding the language on the truck."
In Fort Bend County, located southwest of Houston, Hillary Clinton won the majority of the vote in last year's presidential election, with 51 percent versus 45 percent for Trump.
Nehls said he wants to avoid a potential confrontation on the road, where another driver might take offense to the profane anti-Trump display.
"I don't want to see anything happen to anyone," the sheriff said. "With people's . . . mindset today, that's the last thing we need, a breach of the peace."
Nehls - a Republican who is considering a congressional bid, according to the Chronicle - did not immediately respond to a request for comment.
It's not uncommon for bumper stickers to bluntly convey political viewpoints, from messages like "Impeach Clinton" during Bill Clinton's presidency to "Hail to the Thief" after George W Bush's 2000 election win over Al Gore.
While the First Amendment protects the bulk of offensive speech, there have been several past incidents in which law enforcement officials cited drivers for the messages of their bumper stickers.
Typically, those who are cited have bumper stickers with profane language or pictures. A man in Georgia, James Daniel Cunningham, was arrested and fined $200 for his bumper sticker, which read, "(Expletive) happens." The Georgia Supreme Court ruled in 1991 that the state's law banning bumper stickers with offensive messages wrongfully restricted the driver's right to free speech.
A few states still have laws specifically prohibiting offensive bumper stickers. Tennessee law, for example, states: "To avoid distracting other drivers and thereby reduce the likelihood of accidents," displaying obscene or offensive movies, bumper stickers, window signs or other markings on or in a motor vehicle is prohibited, punishable by a fine of up to $50.
In 2011, Tennessee officials said they'd begin ramping up their enforcement of bumper sticker language - though there haven't been many incidents reported. In March 2017, a man was cited for a bumper sticker depicting stick figures having sex, which read, "making my family." He filed a lawsuit against the Metropolitan Nashville Police Department, claiming the sticker does meet the constitution's definition of obscenity.
