Hoosiers

In 1951, Norman Dale arrives in the rural southeast Indiana town of Hickory to become a high school teacher and head basketball coach. He was hired by Cletus Summers, the principal and a longtime friend of Dale's. Dale, just out of the Navy, had been a champion collegiate coach until he struck one of his players. The coaching position in Hickory is a last chance for him.
Like much of the state, Hickory is passionate about basketball. The townspeople are aware that the best player in town, Jimmy Chitwood, does not intend to play on this season's team due to his attachment to the previous coach and the concern of hometown faculty member Myra Fleener, who has been looking after Jimmy since his mother's illness and warns Dale not to try to persuade Jimmy to change his mind.
The school enrollment is so small that Dale has only seven players on his squad. At his first practice, Dale quickly dismisses one, Buddy Walker, for not paying attention and talking while the coach is talking. Another, Whit Butcher, walks out in support of his friend, leaving Dale with only 5 players, the minimum needed to play. He then begins drilling the remaining five players (Rade Butcher, Merle Webb, Everett Flatch, Strap Purl, and equipment manager Ollie McLellan) with fundamentals and conditioning but no scrimmages or shooting, much to the players' dislike. Townsmen who have heard of the coach's non-traditional approach to working with the team intrude on a practice and demand to know what Dale is doing. However, Whit's father arrives with his son in tow and makes his son apologize to Dale for walking out and ask for another chance. Mr. Butcher then shows his support of Dale by ushering the townsmen out of the gym.
With the team having worked on a four-pass offense, Dale remains committed to this approach in the opening game of the season, even when Rade Butcher disobeys him and repeatedly shoots successfully without passing. Dale benches him and, when another player fouls out, refuses to let Rade return to the game, leaving his team with only four players on the floor to the jeers of the home crowd. In a subsequent game, when an opposing player pushes his finger into Dale's chest during an on-court argument during a timeout, Rade jumps to his defense and hits the player on the jaw. After the ensuing brawl, Cletus, who has been assisting Dale in coaching, suffers a mild heart attack.
The coach further alienates the community by having the team play with a slow, defensive style that does not immediately produce results and also by losing his temper, causing him to be ejected from multiple games.
With Cletus laid up, Dale invites knowledgeable local former star basketball player Wilbur "Shooter" Flatch, Everett's alcoholic father, to join him on the bench as a new assistant. This too confounds the town, including Everett. The coach has one major stipulation in order for Shooter to participate with the team: he must be sober at all times around the boys.
By the middle of the season, an emergency town meeting is called to vote on whether Dale should be dismissed. Fleener appreciates the coach's having stayed away from Jimmy and his efforts with Shooter and, despite having learned of Dale's past mistake and volatile behavioral pattern as a coach, she unexpectedly expresses support for him at the meeting. Just as the vote is being counted, Jimmy enters the meeting and asks permission to speak. He says he's ready to begin playing basketball again, but only if Dale remains as coach. The ballot count is reported and it has gone against Dale, but Fleener's mother jumps up and calls for a re-vote. Mr. Butcher calls for a voice vote from the assembly, and the townspeople overwhelmingly vote for Dale to stay as coach.
From this point, Hickory becomes a nearly unstoppable team. Along the way, Dale proves Shooter's value to the townspeople (and to Shooter himself) by intentionally getting himself ejected from a game and forcing Shooter to show his coaching ability. Shooter does just that by diagramming a play by which Hickory wins the game on a last-second shot. Despite a setback in which Shooter arrives drunk to a game and ends up in a hospital, the team advances through tournament play with contributions from unsung players, such as the pint-sized Ollie and devoutly religious Strap.
Hickory shocks the state by reaching the championship game in Indianapolis. In a large arena and before a crowd bigger than any they've seen, the Hickory players face long odds to defeat the defending state champions from South Bend, whose players are taller and more athletic. But with Chitwood scoring at the last second, tiny Hickory takes home the 1952 Indiana state championship.

Question: What was the cause of the argument that prompted Rade to hit another player in the jaw?
Answer: An opposing player pushed his finger into Dale's chest