The message on the receipt rattled Sadie Karina Elledge, but it made her grandfather see red.

Instead of leaving a gratuity on Monday, a couple eating at the Harrisonburg, Virginia, restaurant where Sadie works scrawled: “We only tip citizens.”

The dig was aimed at Sadie, 18, who was born in America, but is of Honduran and Mexican descent. So, John Elledge took a photo of the grease-stained receipt left for his granddaughter and posted it on Facebook.

Beneath the photo he typed: “You are a complete and total piece of dung.”

Elledge, who is white, told The Washington Post he’s particularly sensitive to slights directed at his multicultural family.

After “flunking out of college,” Elledge spent most of the 1980s in Honduras, working for the Episcopal church. He taught English to children in a bilingual school, started a youth program and met Iris, the Honduran woman who would become his wife.

She already had two children, so he adopted them and they returned to the United States. The family settled in Harrisonburg, a Virginia city ringed by three universities.

After Elledge posted the receipt on social media, the story spread quickly among his friends, including a few lawyers and investigators who tried to identify the person who scrawled the signature at the bottom of the receipt.

But before they could figure it out, the people who ordered the gyro and the drinks returned to the restaurant, angered after seeing the post.

About that time, John Elledge walked into the restaurant. He’d heard the people who wrote the nasty message to Sadie were back, and marched to the restaurant to meet them face to face.

“We didn’t talk much,” Elledge told The Post.” She was mad that I posted it … the guy, he was being really belligerent.”

“… She was asking me why I posted it,” Elledge said. “I said obviously, it was an insult (above) your signature against my granddaughter, darn right I’m going to post it. And no apologies.”