Who knew the biggest moment of NFL Sunday would be the national anthem?

Many social media users symbolically 鈥渢ook a knee鈥� with NFL players to protest racial inequality, while others joined U.S. President Donald Trump in condemning the athletes for their silent gesture during the singing of the U.S. national anthem on Sunday.

Dozens of players either knelt or linked arms in solidarity ahead of Sunday鈥檚 games, in response to Trump鈥檚 call on Friday for owners to 鈥渇ire鈥� anyone who refused to stand for the anthem. Trump鈥檚 words triggered a heated response from many athletes and team owners, including some who have supported him in the past. New England Patriots owner Robert Kraft, for instance, expressed his 鈥渄eep disappointment鈥� in a statement, while Jacksonville Jaguars owner Shad Khan 鈥� who once donated to Trump鈥檚 campaign 鈥� joined his players in locking arms on the field.

Trump鈥檚 initial comment came during a rally in Alabama, but he doubled down on his rhetoric on Twitter the next day. Trump tweeted several inflammatory remarks about NFL players on Saturday night and Sunday morning, amid other complaints about Iran, North Korea and his political rivals.

鈥淚f NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!鈥� Trump said in one of his . 鈥淣FL attendance are ratings are WAY DOWN. Boring games yes, but many stay away because they love our country. League should back U.S.鈥�

The kneeling gesture started last year with NFL quarterback Colin Kaepernick, who took a knee to protest the treatment of black Americans by police. Other players in the league, which employs a majority of black players, have also done so to protest racial inequality and injustice in the United States.

A number of teams protested during the anthem on Sunday, including more than a dozen members of the New England Patriots. The Pittsburgh Steelers didn鈥檛 take the field until after the anthem.

Trump later tweeted about the show of solidarity, saying those who stood with locked arms were "good," while "kneeling not acceptable."

Many social media users came out loudly in support of players who chose to take a knee, highlighting the fact that it is their right to do so as residents of a free and democratic society. Individuals from all corners of society, including sports, entertainment and politics, offered their support for the gesture on Twitter. Several veterans also defended the players鈥� right to free speech.

Meanwhile, others loudly derided the athletes for what they called 鈥渦npatriotic鈥� behaviour from 鈥渟poiled鈥� athletes.

Trump has also raised the ire of several high-profile NBA stars over the weekend, including LeBron James, Kobe Bryant and Steph Curry. Trump rescinded an invite to Curry who is a part of the championship-winning Golden State Warriors over the weekend, after Curry balked at the idea of meeting with Trump at the White House. The championship-winning team traditionally meets the president at the White House but after the back and forth between Curry and Trump, the Warriors said the team would no longer be visiting the White House.

Also on Sunday, Oakland Athletics player Bruce Maxwell took a knee as a gesture of solidarity with other athletes, marking the first time an MLB player has done so.

But while members of the NBA, NFL and MLB showed their solidarity in the face of Trump鈥檚 comments, the NHL鈥檚 Stanley Cup champion Pittsburgh Penguins announced they would accept Trump鈥檚 invitation to the White House.

鈥淭he Pittsburgh Penguins respect the institution of the Office of the President, and the long tradition of championship teams visiting the White House,鈥� the team said in a on Sunday, amid the #TakeAKnee outcry. 鈥淎ny agreement or disagreement with a president鈥檚 politics, policies or agenda can be expressed in other ways. However, we very much respect the rights of other individuals and groups to express themselves as they see fit.鈥�

The Penguins鈥� decision was loudly criticized, with many pointing out that only one member of the team - defender Trevor Daley - belongs to a visible minority.

Trump applauded the Penguins as a "great team" on Twitter after they accepted his invitation.