For more than a decade the 100-foot-long wall that separates Portland’s East End wastewater treatment plant from a popular paved trail has been open to the whims of graffiti artists. In the name of open expression, it is not policed by city or water district officials, who have left the wall to be self-governed by the people who use it, with each new display staying up for as much or as little time as it takes the next artist to paint over it.

That’s the way it’s been, and that’s the way it should be, even after a mural, painted by an anonymous artist, appeared there last week depicting Gov. Paul LePage in Ku Klux Klan regalia next to the words “racist,” “homophobe” and “moron.”

Despite handwringing from public officials over whether the artwork should be removed, public action wasn’t necessary — over a few days, the mural was painted over then altered.

Overall, some people agreed with the mural, others found it offensive, and both sides were able to express their views, both through the media and on the wall itself. It was free speech used in the service of public discourse.

Even with free speech, of course, there are limitations. Public expression, in whatever form, should not incite violence or spread false, malicious claims.

But the mural was neither of those. It was simply an anonymous artist speaking his or her mind on one of the most powerful people in the state, someone whose every word and action leads the nightly news and headlines the morning paper.

You can argue that the artist was wrong, and that he or she misused KKK imagery to inflate the providence and impact of the governor’s remarks on race. Or you can say that depiction was right on, a necessary shock to show the hurt and hate validated by LePage’s comments.

Either way, it’s important that spaces exist where these ideas can be expressed and argued without official interference. The wall in Portland is one of those spaces.

Whatever you think of the mural, it provoked a response. Some people applauded, others cringed or got angry. Some people contacted news outlets, or wrote online comments. A few went to the spot to paint over the picture or change it, expressing their view in the same medium as the original artist.

That’s the First Amendment in action — welcoming to a wide range of public expression, if sometimes messy and even irritating.

At a time when people can avoid news that doesn’t comfort them or confirm their pre-existing notions, we could all use a little more of that messiness.