In an interview with EWTN's Raymond Arroyo on Thursday, Cdl. Müller, former prefect of the Congregation for the Doctrine of the Faith, called on the Pope to "look for reconciliation" with Abp. Viganò.
Viganò, former papal nuncio to the United States, has been in hiding since publishing his bombshell 11-page letter alleging Pope Francis lifted sanctions from ex-Cdl. Theodore McCarrick, despite knowing he is a serial sexual predator who for decades preyed on seminarians and minors.
In addition to urging reconciliation with Viganò, the German cardinal called on Francis to "give answers" to the former papal nuncio's "accusations or questions," reminding him that "the people of God have a right to know what happened."
Cardinal Müller added that the Pope must strive to overcome divisions among Catholics and serve as "a symbol of the unity of the Church."
"We must overcome, with the help of the Holy Father, the splitting of the Church between conservatives and so-called liberals," he said. "We are one Church united in the faith and not of conservative or liberal ideology."
Cardinal Müller also addressed the clerical sex abuse crisis, noting that "the Church never changed the teaching that every attack against the Sixth Commandment is a mortal sin."
"As you looked at the cases you considered and investigated, the preponderance of them were what?" Arroyo asked. "Were they predominantly children? Women? Men? Who were the victims in most of these cases you investigated?"
"We can say 80 percent or more of the victims had been young people — but not girls. Boys, bigger than 14 years," Müller replied. "It's more a homosexual attack than a pedophile attack. ... The victims are not — the great majority — they are not children but teenagers and older."
Arroyo followed by questioning the cardinal about claims that the abuse crisis is the product of "clericalism."
"The Pope, in opening the Synod ... said 'clericalism' must be rooted out; it is the source of so many evils," he noted. "And certainly from clerics all over the United States, we keep hearing 'clericalism' is the reason for the sex abuse crisis. In your estimation, is that true?"
"No," Müller answered. "The reason of sexual abuse is always non-respect of the Sixth Commandment."
The cardinal went on to confirm recent reports that the Pope intervened personally to halt a sex abuse investigation of his ally, U.K. Cdl. Cormac Murphy-O'Connor.
Just months into his pontificate, Francis reportedly demanded to meet with Müller, then head of the CDF, to quash an inquiry into allegations against Murphy-O'Connor — a key figure in his election to the papacy.
Reflecting on the incident, the cardinal told Arroyo: "My proposal is to make the congregation in these cases more independent. It's not good that the Pope takes over this right to stop a necessary investigation."
With an eye to the Youth Synod underway in Rome, Müller also remarked that synods have no magisterial authority.
"The Synod of the Bishops is not an ecumenical council — it does not have magisterial authority," he said. "The Pope cannot change the basic constitution of the Church."