The 76ers announced the punishment for the unidentified fan Thursday, one day after the incident took place during Philadelphia's playoff game against Westbrook and the Washington Wizards.
"We apologize to Russell Westbrook and the Washington Wizards for being subjected to this type of unacceptable and disrespectful behavior," the Sixers said as part of their statement. "There is no place for it in our sport or arena."
The NBA also released a statement Thursday, saying an "enhanced fan code of conduct will be vigorously enforced" at arenas during the playoffs.
"The return of more NBA fans to our arenas has brought great excitement and energy to the start of the playoffs, but it is critical that we all show respect for players, officials and our fellow fans," the league said. "An enhanced fan code of conduct will be vigorously enforced in order to ensure a safe and respectful environment for all involved."
In addition, the National Basketball Players Association released a statement calling on fans to "Respect our Players. Respect our Game."
"True fans of this game honor and respect the dignity of our players," the statement read. "No true fan would seek to harm them or violate their personal space. Those who do have no place in our arenas. And their conduct is appropriately evaluated by law enforcement just as if it occurred on a public street."
Westbrook left the game Wednesday after suffering an ankle injury in the fourth quarter and was limping toward the tunnel when the fan dumped the popcorn on the nine-time All-Star.
A furious Westbrook had to be held back by multiple Wizards staffers and arena security guards before heading back down the tunnel. The fan was ejected by security moments later.
"To be completely honest, this s--- is getting out of hand, especially for me," Westbrook said after Washington's 120-95 loss. "The amount of disrespect, the amount of fans just doing whatever the f--- they want to do -- it's just out of pocket. There are certain things that cross the line. Any other setting ... a guy were to come up on the street and pour popcorn on my head, you know what happens.
"In these arenas, you got to start protecting the players. We'll see what the NBA does."
Teammate Bradley Beal called the incident "disgusting," and Wizards coach Scott Brooks said the individual should be banned from the league.
Valerie Camillo, president of business operations for the Wells Fargo Center, released a statement shortly after the game that read: "This was classless, unacceptable behavior, and we're not going to tolerate it at Wells Fargo Center. We're proud to have the most passionate fans in the country and the best home-court and home-ice advantage around, but this type of behavior has no place in our arena."
Four years ago, a fan sitting courtside in Philadelphia was ejected for flipping off Westbrook. In 2019, a fan in Utah was banned from Vivint Smart Home Arena for life after getting into a verbal altercation with Westbrook while he was on the Oklahoma City Thunder bench.
ESPN's Brian Windhorst contributed to this report.