The unruly fan behavior is not limited to the N.B.A. Baseball stadiums have hosted a number of fights between fans since beginning its season this spring.

Samuel R. Sommers, an associate professor of psychology at Tufts University and an expert on the psychology of fans, said that sports bring people together in both unifying and combative ways.

“Take your pick, whether we’re talking a return to normalcy or whether we’re talking about people getting the pent-up energy out of their system,” Sommers said. “Things like this happen when you get groups of people like this together and when you add the excitement, the adrenaline, the energy of sports.”

This week’s episodes resurfaced a trend of troubling fan interactions at N.B.A. arenas that the pandemic had paused. In 2019, the N.B.A. toughened its fan conduct code after lobbying from players amid high-profile incidents, including the Toronto Raptors’ Kyle Lowry being shoved by Mark Stevens, a Golden State Warriors minority owner, during a finals game.

Players like Westbrook and Young have largely showed restraint when receiving vitriol from fans.

“Obviously I’m doing something right if you hate me that much,” said Young, who cursed back at fans after his playoff debut against the Knicks. “At the end of the day, we’ll get the last laugh if we do that.”

Westbrook said that he had learned to look the other way during most cases but that the situation was worsening. Three years ago, the Jazz barred a fan in Utah for, the team said, “excessive and derogatory verbal abuse directed at a player.” Westbrook, who is Black, said that fan, who appeared to be white, made “disrespectful” and “racial” comments.

This week, Nets guard Kyrie Irving, in comments to reporters, appeared to be trying to pre-empt any personal or racial attacks before playing against his former team, the Boston Celtics, in Game 3 of their series at TD Garden on Friday.