The most recent in what has become a reprehensible series of attacks on Muslims should offend all Americans.

In the Twin Cities, a suburban school board member apparently called Muslim students “unsanitary’’ on social media. And on Sunday’s “Meet the Press,” a Republican presidential candidate said no Muslim should ever be elected president because that religion somehow violates the U.S. Constitution.

It is bad enough when an average citizen shouts “get rid of all Muslims’’ at a presidential political rally. But it’s especially shameful when biased, religion-bashing comments come from current or aspiring public officials. Our leaders, of all people, should be active, strong defenders of freedom of religion, inclusion and diversity.

In the local case, Columbia Heights school board member Grant Nichols should resign. Last week, his board narrowly voted to let Nichols keep his seat despite revelations that he commented on the bathroom habits of Muslims in a Facebook post.

Any school leader who singles out a group of kids for that kind of public criticism cannot be an effective student advocate. Nor can he work well with school staff members and families who were appalled by his comments and want him to step down.

The school district’s attorney told the Star Tribune that Nichols, 40, admitted to others that he had written the post. But he later denied it, saying that someone must have used his phone to post the comment.

The incident unfolded in a working-class community north of Minneapolis with 20,000 residents and a school population of about 3,100. According to the district website, the enrollment is 38 percent African-American, 30 percent Hispanic, 24 percent white, and 8 percent Asian or Native American. Just over 40 percent of the students come from families where English is not the primary language spoken at home.

Parents and students of all backgrounds urged the board to vote Nichols out of his post last week. When that effort failed, Muslim students walked out of school in protest, along with many of their classmates and school staff members. They stayed outdoors for about 45 minutes, then returned to class. On Friday, Gov. Mark Dayton visited the district, called for Nichols’ resignation and praised students for taking a stand.

Imagine how those students felt when they learned that Ben Carson said he doesn’t believe a Muslim should be elected president. During a Sunday interview, he said the Islamic faith goes against the values of the U.S. Constitution.

Ridiculous statements like that only demonstrate Carson’s ignorance about both Islam and the Constitution. Like most religions, Islam does not advocate hate or killing. And though it has not always been practiced fairly, one of the bedrock founding principles of this nation involves freedom of religion.

GOP front-runner Donald Trump also seems uncomfortable with the possibility of a Muslim in the White House. In fact, he said Sunday on NBC that a Muslim president “is something that could happen. … Some people have said it already happened, frankly” — an apparent reference to President Obama. In subsequent interviews, he seemed to qualify his remarks by distinguishing between all American Muslims and extremists.

Leaders and would-be leaders who use religion to appeal for public support — or even simply to make inflammatory remarks on Facebook — should be held accountable by voters and governing boards. Americans expect, deserve and should demand better.