[FlasherZ]

Originally Posted by Robert Goodman

Anybody here know what that was about? Safety? Or were they in play, so you wouldn't need throw-ins?

https://vault.si.com/vault/1991/11/1...-from-the-fans

Salient points:

At the time, the cage made good sense. Front-row spectators sat even closer to the court than they do today, and Naismith's original rules said that when the ball went out of bounds, the first player who got to it could throw it back in. Obviously, it would have been disastrous to allow players to wrestle in the laps of paying customers for possession of the ball. With the cage the rule was moot—the ball never went out of bounds.
[...]
Many eastern professional teams played in cages until 1925, and a few continued using them well into the '30s. Cages were rarely used outside the Northeast and never by high school, college or AAU teams. Still, the term eager was commonly used to describe all basketball players.
[...]
The original reason for using a cage was largely forgotten by the 1920s; many professionals of the time believed its purpose was to protect players from enraged fans. They had ample reason: Pro basketball in the '20s was no place for shrinking violets. It was considered fair play to drive the man with the ball into the wire or rope, especially if he was shooting. When a home-team player was thus clobbered, it was not unusual for fans to join the resulting fray. The players entered and left the cage through doors at either end, and fans sometimes fought their way in using the same openings.

So, no... the bad behavior of fans isn't new to the game.