Facebook has apologized for what it called a "mistake" in rejecting a theology ad from Franciscan University of Steubenville, on the grounds that an image of the cross was too violent and sensational.

"Your image, video thumbnail or video can't contain shocking, sensational, or excessively violent content," was Facebook's response, according Tom Crowe, web communications director for Franciscan University of Steubenville.

Used to promote Steubenville's master's programs in theology, catechetics, and evangelization, the image was of the San Damiano Cross, a 12th century cross most commonly associated with the university's patron, Saint Francis of Assisi.

On Monday, a Facebook spokesperson apologized for the error, stating "sometimes we make mistakes."

"This image does not violate our ad policies. We apologize for the error and have already let the advertiser know we approved their ad," the spokesperson continued.

Since other ads with this image have been approved, Crowe told Fox News it was likely that this was not "systemic religious bigotry" but a one-off mistake, possibly from a low-level Facebook employee with a grudge against Christianity.

"Facebook approved other ads with the exact same image, which again leads me to believe it wasn't an algorithm, but was a low-level staffer who skims many, many ads and just had something personal against this one," he said.

Crowe was never given the exact reason behind the error, but the mistake did spur him to write a reflection on the culture's view of the cross and its rejection of Christ.

"The San Damiano Cross. Jesus in glory, reigning from his cruciform throne. This is what the monitors at Facebook consider excessively violent, sensational, and shocking," he wrote in an article on the university's website, titled "He was Rejected."

"And indeed, the Crucifixion of Christ was all of those things. It was the most sensational action in history: man executed his God."

However, Crowe said, the violence only emphasizes Christ's love for humanity.

"It was not the nails that held Jesus to the cross: he was God, he could have descended from the Cross at any moment," said Crowe, quoting Catholic author Fr. Mike Schmitz.

"No, it was love that kept him there. Love for you and for me, that we might not be eternally condemned for our sins but might have life eternal with him and his Father in heaven."