"Wouldn’t you love to see one of the NFL owners, when somebody disrespects our flag, to say 'Get that son of a b---- off the field right now?'" Trump said.
On Twitter, Trump defended his comments, saying that "Courageous Patriots have fought and died for our great American Flag."
Trump's comments spurred a backlash that included protest against the "Star Spangled Banner" across several NFL teams on Sunday. Several veterans who fought in the U.S. armed forces echoed the players' sentiments.
The tweet -- which included a photo of the farmer from Willard, Missouri, kneeling on the ground accompanied by what Gilmore said was his grandfather's phrase "those kids have every right to protest" -- was retweeted nearly 130,000 times in just a day.
The hashtag #VeteransForKaepernick began trending after people took notice that the former quarterback, who currently isn't signed to a NFL team, was not standing for the national anthem. After Sunday's gameday protests, veterans took to Twitter again using the hashtag along with a new one, #TakeAKnee.
However, in the past, Villanueva has expressed solidarity with Kaepernick, saying in a 2016 interview, "I will be the first one to hold hands with Colin Kaepernick and do something about the way minorities are being treated in the United States, the injustice that is happening with police brutality, the justice system, inequalities in pay," according to ESPN.
Even as the protests he inspired become more widepsread, Kaepernick remains unsigned in the NFL. He opted out of his contract with the 49ers after last season.