Americans protesting against China during an NBA preseason basketball game in Washington, D.C., were shut down by security, all while the U.S. national anthem played in the background.

The surreal scene was circulated on social media with video of security taking away protest signs.

The Capitol One Arena security member said that spectators in attendance were not allowed to display a political opinion.

Protesters chose the game because it was a preseason match between the Washington Wizards and the Guangzhou Long Lions of the Chinese Basketball Association.

The NBA has been criticized for shutting down employees who spoke out against China.

"We are currently standing tall behind the basket with our Free Hong Kong shirts on. We were told if we do another sign we will be removed. Standing tall in our tshirts," tweeted John Schweppe, one of the protesters.

Later that sign was confiscated as well.

A human rights group called "Victims of Communism" handed out "Free Hong Kong" shirts outside the entrances of the stadium for the game.

Others protested in the audience and tweeted about their experience, including Cesar Conda, the former chief of staff to Sen. Marco Rubio (R-Fla.).

"So the Wizards security just kicked out two people in the Second level for chanting Free Hong Kong. I just saw it," he said.

The Washington Wizards trounced the Guangzhou Loong Lions, 137 to 98.

Here's more about the NBA controversy:

Why the NBA Is Facing a Difficult Choice in China | WSJ www.youtube.com