“I would have absolutely no right to speak up except that he repeatedly brandishes the Bible and calls himself a Christian,” said preacher and best-selling Christian author Max Lucado, explaining why he publicly criticized Donald Trump in an item on his personal blog. He doesn’t even put a candidate’s bumper sticker on his car, he said in an interview with Christianity Today, and this blog item was only the third time in 30 years he’d spoken on a political matter.

Lucado, whose almost 100 books have sold an estimated 80 million copies, is the long-time pastor of Oak Hills Church in San Antonio, a non-denominational church once affiliated with the Churches of Christ. Christianity Today has called  him “America’s pastor.”

The reason he spoke up was Trump’s claim to speak as a Christian and a divine “nudging,” he told CT.

It’s a high stakes thing from my perspective because people make decisions about Christ on the basis of Christians and how we behave. If he’s going to call himself a Christian one day and call someone a bimbo the next or make fun of somebody’s menstrual cycle, it’s just beyond reason to me.

He always interviewed the men his daughters were dating, he said on his blog on Wednesday, making sure the man was “a decent guy.” But Trump is not a decent guy:

He ridiculed a war hero. He made mockery of a reporter’s menstrual cycle. He made fun of a disabled reporter. He referred to the former first lady, Barbara Bush as “mommy,” and belittled Jeb Bush for bringing her on the campaign trail. He routinely calls people “stupid,” “loser,” and “dummy.” These were not off-line, backstage, overheard, not-to-be-repeated comments. They were publicly and intentionally tweeted, recorded, and presented.

Such insensitivities wouldn’t even be acceptable even for a middle school student body election. But for the Oval Office? And to do so while brandishing a Bible and boasting of his Christian faith? I’m bewildered, both by his behavior and the public’s support of it.

Lucado also touched on the source of Trump’s appeal and was equally unpleased. “The stock explanation for his success is this: he has tapped into the anger of the American people,” he wrote. “As one man said, ‘We are voting with our middle finger.’ Sounds more like a comment for a gang-fight than a presidential election. Anger-fueled reactions have caused trouble ever since Cain was angry at Abel.”

The Washington Post published a slightly longer version on its website on Friday afternoon. In that version, he compared Trump’s public presence to President Obama’s and rejected the idea that Trump is simply being honest when he speaks.

“For out of the overflow of the heart the mouth speaks,” Jesus said. Words are a heart monitor. Christians would do well to summon any Christian leader to a higher heart standard. This includes pastors (especially this one), teachers, coaches and, by all means, presidential candidates.

A president is not “pastor-in-chief,” he told CT, but, “We do elect a commander-in-chief to set a respectable standard for our nation and to be the kind of man or woman that we would respect when they speak. … We pay a high price as a people if we don’t hold our leaders to a high standard.”