Rich, one half of the Big & Rich and owner of Lower Broadway's Redneck Riviera honky-tonk, followed it up with a picture of his soundman after cutting out the Nike logo from his socks.
The singer, whose signature hit with the multi-platinum selling Big & Rich is "Save a Horse (Ride a Cowboy)," followed it up saying to watch Nike stock by this time next week and responded to several tweets responding to the cut up socks.
Kaepernick, who remains a free agent after last playing in the NFL in 2016, will be one of the faces of Nike's 30th anniversary of the "Just Do It" campaign.
The quarterback has become a polarizing figure due to his protests of police brutality and social inequality during the playing of the national anthem at NFL games. He sat and kneeled during the anthem in the 2016 preseason and continued the protest through the rest of that season.
During that preseason, Kaepernick wore socks depicting cops as pigs. Something which Rich referenced in his many tweets criticizing the company.
The Nike "Just Do It 30th" Anniversary ad and the NFL
"Believe in something,” the advertisement reads in white letters in front of a black-and-white portrait of Kaepernick. “Even if it means sacrificing everything.”
The ad arrives ahead of the NFL season, marked by controversy over the league's response to the protests inspired by Kaepernick. The quarterback has also filed a grievance against the NFL, alleging that owners have purposefully denied him employment.
"We believe Colin is one of the most inspirational athletes of this generation, who has leveraged the power of sport to help move the world forward," Gino Fisanotti, Nike's vice president of brand for North America, told ESPN.
Nike is the NFL's official apparel sponsor and manufactures the jerseys and game day apparel worn by all 32 franchises.
USA Today contributed to this report.