I love this story....
The Bears were also a reflection of a tough town and of their founder George Halas. Their contests with the Steelers sometimes exploding into a collision of two tough guy cultures. Just think about 2005, Jerome Bettis and Brian Urlacher, and you get the idea. In '69 neither of these teams were going anywhere as they met at Wrigley Field in Chicago (Pittsburgh and Chicago were involved in the coin flip for who would have first pick in the 1970 draft. The Steelers won and netted Terry Bradshaw). The game degenerated into a series of fights. In these more modern times such a thing would not be allowed, but at that time you have to imagine a level of tolerance that might be closer to that of what we see with ice hockey.
One of my memories from watching that game on television was Steeler safety Charlie Beatty, a college teammate of Greene's being cut off from his teammates by a couple of Bear's linemen who then pummeled and stomped him. But the main event involved Greene and Bears middle linebacker Dick Butkus. For younger readers or just those new to the sport, Butkus was the Ray Lewis of his era, feared by everyone. Well, everyone except Greene apparently. Gary Pomerantz describes what happens in his book Their Life's Work.
Chicago linebacker Dick Butkus, blocking for punt returner Gayle Sayers, blindsided the oncoming Greenwood, knocking him unconscious near the Steelers' bench. Butkus stood over the fallen rookie like Ali stood over Liston. Onto the field stepped Greene. Eye-to-eye with Butkis, Greene threatened him and spat in his face. "Butkus was standing there with this [spit] thing hanging down his face mask," Mansfield said. Mansfield thought, This is going to be the greatest fight in the history of the NFL! But Butkus turned and walked away. Decades later, Mansfield said, "That was the beginning of the end of the Pittsburgh Steelers' problems."
So you must understand when it was said that teams feared Greene, they meant that they were actually scared. Ernie Holmes stated that during the course of Super Bowl IX that Minnesota Vikings center Mick Tinglehoff was literally trembling (Holmes derisively referred to him as "Ticklehoff"). And who can blame him.
Examples are numerous. In the America's Game program on the 1975 Steelers Greene is shown grabbing a Cleveland Browns offensive lineman by the shoulder and kicking him in the groin. In a 1977 playoff game in Mile High Stadium in Denver, he knocks a Broncos offensive lineman who has been holding him out of the game with a punch to the gut. ESPN's Tom Jackson describes another incident when Greene moved toward the Denver bench in anger and the whole Broncos team recoiled in fear.