The trash-talking Air Force veteran who shot to fame on the right last year after raising more than $20 million on GoFundMe for a privately funded border wall says he is on a mission to “save” Texas from “illegals”—but some nefarious butterfly aficionados keep getting in his way.

Triple-amputee veteran Brian Kolfage, whose group We Build the Wall got a shiny endorsement from the Department of Homeland Security this week, built a portion of the private wall in New Mexico before moving on to the Rio Grande Valley in Texas, which he has claimed is “under siege by cartels, criminals and illegal aliens.”

But it seems Kolfage has reserved his ire not for the cartels or even undocumented immigrants, but the National Butterfly Center, a 100-acre butterfly sanctuary near Mission, Texas, where he claims “butterfly freaks” are standing in the way of his wall.

The feud centers on whether the wall Kolfage is trying to build nearby will affect the flow of the Rio Grande. Kolfage’s group, We Build the Wall, appears to have started clearing vegetation on the land last week.

Bob Crane, a spokesman for the North American Butterfly Association, which operates the center, said his group is worried any wall on the banks of the Rio Grande would exacerbate flooding. A part of the sanctuary flooded during a 2010 tropical storm, according to Crane, and some of the land washed away.

“NABA’s primary concern is that the structure they intend to build will change the course of the Rio Grande when next it floods and that this will result in significantly greater flood impact at the NBC,” Crane wrote in an email to The Daily Beast.

Kolfage and We Build the Wall declined to comment. But Kolfage has taunted and smeared his butterfly-loving foes on Twitter, denouncing them as “freaks,” claiming the sanctuary is a “sham,” and accusing them of ignoring human trafficking. Kolfage has even sent tweets implying that the butterfly sanctuary’s operators are somehow engaged in the international butterfly smuggling trade.

“It’s a big business!” Kolfage tweeted on Nov. 16, linking to an unrelated story about a butterfly smuggler.

Kolfage has also taunted the sanctuary with a rendering of the proposed wall that features abundant butterflies surrounding what he calls the “water-butterfly-wall.”

The butterfly sanctuary’s Facebook page has since been “flooded with harassing messages,” according to Crane.

While Kolfage plans to build his 3.5-mile wall on federal land, opposition from the butterfly center and other critics could hinder his attempts to get construction permits. Because the construction involves the Rio Grande, the wall will likely need approval from the International Boundary Water Commission, which negotiates border water issues with Mexico.

Last week, the IBWC sent a letter to Kolfage’s contractor, Fisher Industries, and We Build the Wall board member and former Kansas Secretary of State Kris Kobach asking them to hold off on construction until they complete an elaborate study of water issues surrounding the wall. Among other things, the IBWC wants to know whether the wall “will impact the floods flows and river flows.”

For now, the ground-clearing can continue, as long as it doesn’t involve actual construction.

“Vegetation in and of itself is not covered by the treaty,” IBWC spokeswoman Sally Spener told The Daily Beast.

This isn’t the first time the butterfly sanctuary has clashed with efforts to build a border wall. Earlier this year, the butterfly refuge’s operators fought to be exempted from any plans for a federally funded border wall. Trump signed legislation in February that would exempt the refuge, and there are currently no plans to build a government border wall on the refuge’s land.

Mariana Trevino-Wright, the butterfly sanctuary’s executive director, has been a vocal opponent of Kolfage’s plans to build on the river. As Kolfage’s crews started to clear plants on the banks last week, Trevino-Wright began trying to draw attention to the work.

“They are secretly and quietly and illegally building this border wall on the banks of the Rio Grande here,” Trevino-Wright told Border Report, a website that covers border news.

Still, Kolfage’s efforts have won supporters in the Trump administration. This week, a Border Patrol official praised the New Mexico barrier constructed by Kolfage’s group, saying she would “welcome” any border wall, including privately owned ones.

Kolfage has also attacked another unlikely foe, a local Catholic priest. Father Ray Snipes runs a church near the proposed wall, and has opposed earlier wall efforts he said would block access to a historic chapel.

Last week, Snipes took Trevino-Wright out on his boat to get a better look at We Build the Wall’s work. Kolfage slammed the priest on Facebook, accusing him of “promoting human trafficking and abuse of women and children” and “driving around in expensive boats.” As Snipes told BuzzFeed, however, he had inherited the boat from another priest after the priest died.

Still, Kolfage has kept up his criticism of both Snipes and the butterfly sanctuary, claiming that the refuge features a “rampant sex trade.”

“HUMAN lives are more important than a butterfly,” Kolfage tweeted on Nov. 19.

Crane pushed back on Kolfage’s claims.

“Mr. Kolfage’s statements are a pack of lies, similar to what he says about anyone opposing these activities, and simply illustrate the type of person that is,” Crane said in an email.