A T-shirt being distributed by Denver’s police union that refers to Democratic National Convention protesters was supposedly a joke.

“We get up early to beat the crowds” and “DNC 2008.”

Get it? “Beat” the crowds?

Count us among those who don’t find it very funny.

The shirt, which features a menacing depiction of a baton-wielding officer, undermines the efforts the Denver Police Department has made to boost its credibility in the community.

It also accomplishes something we thought would be difficult if not impossible: It cedes the moral high ground to Re-Create 68 agitator Glenn Spagnuolo.

That’s because the shirt also is emblazoned with a “68” with a slash through it — a reference to Spagnuolo’s protest group.

It’s true that Spagnuolo made a pest of himself in the months leading up to the August convention in Denver. He hinted darkly about violence and disruption.

And he boasted that Re-Create 68 would be 50,000 strong and would illegally occupy Civic Center park on a day when another group had legitimately obtained a permit to use the park.

Once the convention got underway, it was apparent that Spagnuolo’s predictions were either a product of wishful thinking or delusions of grandeur.

Protest crowds were far smaller than anyone predicted, and while a march did cross through the park, it was far from the mass sit-in predicted.

Overall, we thought law enforcement was effective in giving protesters the opportunity to exercise their First Amendment rights and march with little disruption to the rest of those who were in town for the convention.

It was, generally speaking, a peaceful four-day event.

Unfortunately, this T-shirt is an affront to the hard work of the officers who labored under difficult conditions to make that happen.

Brian Maass, a reporter for local CBS affiliate KCNC-Channel 4, reported earlier this week the shirts were being sold for $10 each by the Denver Police Protective Association, the union that represents most of Denver’s 1,400 police officers. The shirts also had been given free to every Denver officer.

Maass quoted a police detective who said such shirts are traditionally created as a commemorative item after a big event. So far, so good.

But why create something with such an offensive overtone?

Denver police leadership has been working hard in recent years to improve both its use-of-force practices and its image within the community after several controversial shootings.

This T-shirt, no matter how tongue-in-cheek it was supposed to be, diminishes those efforts.

Perhaps the folks in the police union who initially got a giggle from the shirt’s double entendre will now see why it’s not that funny after all.