In the following passage, Shoghi Effendi—or rather his secretary—explains the harsh treatment awaits the Bahá’í who attacks Bahá’u’lláh:

“When a person declares his acceptance of Bahá’u’lláh as a Manifestation of God he becomes a party to the Covenant and accepts the totality of His Revelation. If he then turns around and attacks Bahá’u’lláh … he violates the Covenant. If this happens every effort is made to help that person to see the illogicality and error of his actions, but if he persists he must, in accordance with the instructions of Bahá’u’lláh Himself, be shunned as a Covenant-breaker.”

—from a letter dated March 30, 1957 on behalf of Shoghi Effendi, “Messages to Canada,” pg. 64

This passage indicates that a Bahá’í, having declared his or her belief in Bahá’u’lláh as a consenting adult at—say—age 15, has no right to turn around and criticize Bahá’u’lláh. Such a Bahá’í—or Ex-Bahá’í—is to be regarded as “Covenant-breaker,” and—as if that weren’t heinous enough—an illogical.

Apparently it’s illogical to criticize someone that you once worshiped as a child.

Though apostasy is not a capital offense in the Bahá’í Faith, it was no small crime in the eyes of Shoghi Effendi.

“People who have withdrawn from the Cause because they no longer feel that they can support its Teachings and Institutions sincerely, are not Covenant-breakers—they are non-Bahá’ís and should just be treated as such. Only those who ally themselves actively with known enemies of the Faith who are Covenant-breakers, and who attack the Faith in the same spirit as these people, can be considered, themselves, to be Covenant-breakers.”

—from a letter dated March 30, 1957 on behalf of Shoghi Effendi, “Messages to Canada,” p. 64

Hence belief in Bahá’u’lláh is not a prerequisite for Covenant-breaker status. The only prerequisite is that one is or once was a believer. The key point is keep your mouth shut. You can’t be blamed for ceasing to believe, but to openly criticize the Bahá’í Faith—having once believed—is the most reprobate of offenses.

The following is a specific reference to a Bahá’í who turned against the Bahá’í Faith in its entirety. Abdu’l-Husayn Ayati had been an eminent Bahá’í historian. `Abdu’l-Bahá’ had named him “Avarih,” and Shoghi Effendi declared him a Covenant-breaker for his criticisms of the Bahá’í Faith:

“Avarih … will be condemned by posterity as being the most shameless, vicious, relentless apostate in the annals of the Faith, who, through ceaseless vitriolic attacks in recorded voluminous writings and close alliance with its traditional enemies, assiduously schemed to blacken its name and subvert the foundations of its institutions.”

—Shoghi Effendi, Messages To The Bahá’í World: 1950-1957, pages 53-54

Shoghi Effendi often spoke of apostasy of as though it is an evil in and of
itself. Let’s close with several examples:

“Some have apostatized from its principles, and betrayed ignominiously its cause.”

—World Order of Bahá’u’lláh, page 195

“The volumes which a shameless apostate composed and disseminated, during that same period in Persia, in his brazen efforts not only to disrupt that Order but to undermine the very Faith which had conceived it,…”

—God Passes By, page 327.

“Apostates, rebels, betrayers, heretics, had exerted their utmost endeavors, privily or openly, to sap the loyalty of the followers of that Faith, to split their ranks or assault their institutions.”

—God Passes By, page 408.