For hitting pass receivers in the head, two professional football players have been ordered to explain themselves to Pete Rozelle, an angry commissioner. The pro basketball boss, Larry O'Brien, has fined his game's biggest star, Kareem Abdul-Jabbar, $5,000 for a one-punch assault. Good.

Boys will be boys. And boys playing games will go on hitting each other in the nose. But the league commissioners now are telling the boys that the cost of their foolishness will be high. Proathletes often are deaf to sermons on gentility. They are all ears, though, when dollar bills speak, and nothing hurts worse than hearing greenbacks say bye-bye.

Rozelle has told the National Football League players that violence will be punished by fines and suspensions. It takes small imagination to see a defensive back kill a pass receiver. If a forearm swung at a man's head can produce a concussion, it also can snap his neck. Defensive backs harrumph at the thought and say it's a tough game for tough men. But to same a month's pay, perhaps a defensive back can find a way to tackle a pass receiver without aiming a forearm or elbow at the defenseless fellow's head.

Mel Morgan of the Cincinnati Bengals admitted to his excess Monday night. Pittsburgh's John Stallworth caught a pass and headed upfield until Morgan's forearm crashed into his face. An unsportmanlike-conduct penalty was assessed and Morgan said he was sorry. It "wasn't intentional," he said. "It was just a reflex. I was surprised at myself."

Pittsburgh's Mel Blount knocked out Cincinnati's Bob Trumpy five plays later. Fingered by his own coach last summer as part of the "NFL's criminal element" in testimony during the George Atkinson trial, Blount denied any intent to leave Trumpy headless.

"I was going after the ball," Blount said. "I didn't even see Trumpy. I think when they (league officials) see the play, they'll pardon me just like they did Nixon."

Well, as it happens, Richard M. Nixon, the old Whittier College benchwarmer, was ejected from the biggest game of all. Doubtlessly, Blount fumbled the Nixon analogy, but it may not be a bad idea: Exile headhunters to the beach at San Clemente, where they can do no more harm.

Morgan and Blount are to report to Rozelle's office Monday. He'll hear their stories and then, most likely, fine both players. He should make the fine a figure that speaks loudly.

O'Brien acted without hearing Abdul-Jabbar. Film of the assault was enough evidence. Less than three minutes into the season-opening game the other night, Abdul-Jabbar deliverd a righthand punch to the side of Kent Benson's head.

Abdul-Jabbar was ejected. His right hand was broken. Benson went down from the blow, suffered a mild concussion and lacerations, and played no more that night or the next.

Unlike the football incidents where unbridled aggressiveness led to harm, Abdul-Jabbar's one punch knockout was a piece of instant revenge. As such, it was understandable if not forgiveable.

"If they fined Kareem $5,000, they should have fined Benson $10,000," said an NBA coach.

The coach said film showed Benson setting up at the free-throw line on defense, "As Kareem goes by," the coach said, "they bump together. Then Kareem comes back to the line and Benson, with his back to Kareem, hauls off with his right elbow and hits Kareem with a shot you wouldn't believe.

"Kareem doubles up and staggers - staggers - all they way back to the baseline. The ball goes the left side and Benson is watching it. Then Kareem starts back up the lane toward him. Benson is turned sideways, looking to the left, and Kareem taps him on the shoulder with his left hand - and hits him with a shot that puts him down head first, flat out, laying across the lane."

Benson slhould have expected it, the coach said. "Kareem takes so much physical abuse. At some point, like on a flagrant elbow like Benson's, he's going to retaliate. Benson deserved it."

Benson said he'd done nothing "vicious or malicious." He was "just establishing position" and happened to catch Abdul-Jabbar in "a very vulnerable spot (the solar plexus)" with an elbow.

"I was thinking about being harassed and chopped at since I came into the league," Abdul-Jabbar said, "and I couldn't let him do that."

At the cost of a broken hand and $5,000, chances are Abdul-Jabbar would do the same thing again. Territorial imperative demands it.

Still, the fine was a necessary thing and should have included Benson, the instigator.

In any case, the $5,000 figure tells us something about the league's resolve against fights. Three years ago, Dennis Awtrey of the Chicago Bulls grabbed Abdul-Jabbar by the uniform shirt and punched him in the face. The finethen: $50.