Kansas City Chiefs fans celebrate a penalty called on the San Diego Chargers in their NFL football game Sept. 30 (Colin E Braley/AP)

I saw my first NFL game in Arrowhead Stadium. It was practically new when my grandparents, my dad and I headed east early on a Sunday morning for a four-hour drive to Valhalla. I’d never seen any structure that held that many people. Growing up in a small town, I’d never seen that many people, period.

My grandfather wore a suit; my grandmother and I were in dresses. Apparently people dressed up in those days, or we were the only ones and I didn’t notice. That’s a tradition I’m glad didn’t stick. People were also more polite in those days, a tradition I wish had stuck.

Since that wonderful Sunday, I have been a Kansas City Chiefs fan. That’s why I was stunned Sunday to hear that a small number of idiots at Arrowhead cheered when Matt Cassel left the game because of a head injury in Kansas City’s eventual loss to the Baltimore Ravens. Arrowhead has long had a good reputation around the league for smart, faithful fans who put up with bad teams but continue to fill the stadium, wear the gear, and cheer. They are not unlike Redskins fans in that regard.

Eric Winston, one of Cassel’s linemen, gave a calm but scathing statement about the cheers when Cassel was eventually led off the field.

“We are athletes. We are not gladiators. This isn’t the Roman Colosseum. People pay their hard-earned money to come in here. I believe they can boo, they can cheer, they can do whatever they want. . . . There are long-lasting ramifications to the game we play. . . . I’ve already kind of come to the understanding I probably won’t live as long because I play this game. That’s okay. That’s the choice I’ve made, that’s the choice all of us have made.

“But when you cheer somebody getting knocked out, I don’t care who it is, and it just so happened to be Matt Cassel, it’s sickening. It’s 100 percent sickening. . . . I’ve been in some rough times on some rough teams, I’ve never been so embarrassed in my life to play football, than at that moment right there. . . .

“Boo him all you want. Boo me all you want. Throw me under the bus. Tell me I’m doing a bad job, say I’ve got to protect him more . . . but if you’re one of those people who were out there cheering, or even smiled, when he got knocked out, I just wanna let you know — and I want everyone to know — that I think it’s sickening and disgusting. . . . We got a lot of problems as a society if people think that that’s okay.”

We’ve got a lot of problems as a society. I don’t think that’s news. We also tend to paint every bad act with a broad brush. When the Nats were actively encouraging Phillies fans to come to town, I heard a lot about how awful they all were. The truth is, they aren’t all awful. Blanket statements are seldom, if ever, true. St. Louis baseball fans are regarded as some of the best in the league, but you know there have to be one or two bad apples in a stadium full of people. That’s just reality.

Both Chiefs owner Clark Hunt and Coach Romeo Cremmel have taken great pains to come out in support of the Chiefs fan base, saying that the few who cheered do not accurately reflect Chiefs fans or NFL fans. Winston also felt it was necessary to clarify his remarks to say he didn’t meant to tar all 70,000 people in the stands (although in his original statement, he did not). I believe they are correct.

But that doesn’t make it any less disturbing, akin to the death threats Josh Morgan received when he committed a stupid penalty earlier this season that probably cost the Redskins a game. It was stupid. It was not worthy of the death penalty. The Chiefs are 1-4, and Cassel hasn’t exactly been Sammy Baugh. Again, not worthy of the death penalty.

There has been a lot of debate, after the debacle at the National League wild-card game in Atlanta and the Cassel incident, about whether fans are out of control. The answer is no, because that would imply all fans are out of control. The majority are people who manage to attend games while not punching anyone, pouring beer on anyone, or running onto the field.

We live in a brave new world of anonymous sucker punches. Make that a cowardly new world. It’s easy to tweet or comment or cheer an injury because you don’t have to put your name to your idiotic behavior. That’s a fact of life in 2012.

That doesn’t, however, make it right. When you cheer an injured player, you embarrass your fellow fans, and you embarrass most decent people. Shame used to be the velvet rope that kept people in line, but apparently that’s no longer a tradition either. I wish that one would have stuck, too.

For previous columns by Tracee Hamilton, visit washingtonpost.