"So proud of NASCAR and its supporters and fans. They won't put up with disrespecting our Country or our Flag - they said it loud and clear!" Trump tweeted Monday.
The comments came one day after dozens of NFL players took a knee or otherwise protested during anthems across the country in the wake of Trump suggesting teams could fire them for the gesture, which began last year as a way to raise the focus on social injustice.
Several NASCAR team owners and executives said Sunday they wouldn't want anyone in their organizations to protest. Richard Childress, who was Dale Earnhardt's longtime team owner, said of protesting: "It'll get you a ride on a Greyhound bus."
Childress said he told his team that "anybody that works for me should respect the country we live in. So many people gave their lives for it. This is America."
Hall of Fame driver Richard Petty's sentiments took it a step further, saying: "Anybody that don't stand up for the anthem oughta be out of the country. Period. What got 'em where they're at? The United States."
When asked if a protester at Richard Petty Motorsports would be fired, he said, "You're right."
RPM team owner Andrew Murstein later told ESPN he "wouldn't fire someone for expressing their feelings."
"I would sit down with them and say it's the wrong thing to do that and many people including myself, view it as an affront to our great country," he said. "Yes, there are problems here, but they are nothing close to the problems in North Korea and other parts of the world. We must come together as Americans and respect everyone and everything, especially our flag which is still the symbol of the United States, the greatest country in the world."
NASCAR chairman Brian France created a firestorm in the sport when he endorsed Trump last year. France's efforts to quell criticism over what he insisted was a "personal and private" decision were complicated by Trump's continued mentioning of how he received "NASCAR's endorsement."
A few hours after Trump's tweet, NASCAR issued a statement noting that respect for the national anthem "has always been a hallmark of our pre-race events."
"Thanks to the sacrifices of many, we live in a country of unparalleled freedoms and countless liberties, including the right to peacefully express one's opinion," the statement said.
Dale Earnhardt Jr., NASCAR's most popular driver who will retire at the end of the season, tweeted Monday in support of peaceful protest.
"All Americans R granted rights 2 peaceful protests. Those who make peaceful revolution impossible will make violent revolution inevitable-JFK," he wrote.
Another team owner, Chip Ganassi, said he supports Pittsburgh Steelers coach Mike Tomlin's comments. Tomlin said before the Steelers played on Sunday that players would remain in the locker room and that "we're not going to let divisive times or divisive individuals affect our agenda."
Team owner Joe Gibbs, who won three Super Bowls as coach of the Washington Redskins, said of the anthem that, "so much has been sacrificed for our country and our flag. It's a big deal for us to honor America."
"I'm proud of the way we've represented ourselves, and I'm proud of this sport, too," Gibbs said after JGR driver Kyle Busch won at New Hampshire. "I think this sport has a certain way they look at things. I really appreciate that."
NASCAR said 2016 champion Jimmie Johnson had not been invited to the White House for recognition as he had in the past, but that it necessarily wasn't out of the ordinary because of the change in office.
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