Recently, a Seattle-based grassroots group called the Seattle Mideast Awareness Campaign purchased ads on the side of a dozen public buses in the King County, Seattle bus system. The ads featured the image of a destroyed Palestinian home along with the words “Israeli war crimes — Your tax dollars at work.”

The plans to place these ads were considered provocative by many that opposed the group’s campaign, and three other organizations quickly began to make plans to run ads “portraying Israel as the victim of Palestinian terrorism.” Yet despite the controversy, “Metro and County Executive Dow Constantine initially said the ad was consistent with county ad standards and that it would violate the sponsor’s free-speech rights” to cancel the ads.

Yet at the last minute, Constantine chose to reject the placement of the ads on the county’s buses. Constantine claimed that federal and local law-enforcement agencies warned that the bus system “could be vulnerable to disruption” if the ads were placed. The official went on to say that inserting ads that took part in a “vitriolic debate” would insert “new and significant security concerns [that caused the] reassessment,” essentially saying that placing the ads would’ve risked violence against the bus system.

Now, the ACLU of Washington is suing the bus system, claiming that the Seattle Mideast Awareness Campaign’s free speech rights were violated. Local news station King 5 covered the controversy in a special report. Watch it:

Interestingly, the King County Metro bus system has carried provocative messages several times before in the past. In 2005, buses carried ads proclaiming, “”War kills the innocent — Join together to end the Iraq War.” And in 2009 the buses had ads saying “Yes, Virginia … there is no God.” Given that county officials approved these and other provocative ads, which indeed were part of a “vitriolic debate” over the Iraq war and religion, it is curious to see them reject ads protesting US aid to Israel out of the supposed fear that it would incite violence.

ACLU Washington Executive Director Kathleen Taylor made clear at a press conference that the remote threat of terrorism is not sufficient reason to silent the activist group’s dissent. “The purpose of the First Amendment,” Taylor said, “is to protect speech that is difficult to hear and that makes people uncomfortable…Part of being a free society and a democratic society is we as citizens engage in the hurly-burly of free speech. We can’t say, ‘Oh, it’s inconvenient to have free speech.’”