That is true, because the only way we can know God or attain God’s presence is through the Manifestation of God.
When Baha’u’llah said that the Father had come He meant that He came in the “station” of the Father just as Jesus came in the “station “ of the Son, but Jesus was not literally the Son of God anymore than Baha’u’llah was literally the Father (God).
The following passage does not describe Baha’u’llah; it describes God.
“And now concerning thy reference to the existence of two Gods. Beware, beware, lest thou be led to join partners with the Lord, thy God. He is, and hath from everlasting been, one and alone, without peer or equal, eternal in the past, eternal in the future, detached from all things, ever-abiding, unchangeable, and self-subsisting. He hath assigned no associate unto Himself in His Kingdom, no counsellor to counsel Him, none to compare unto Him, none to rival His glory.” Gleanings From the Writings of Bahá’u’lláh, p. 192
No Manifestation of God has the following Attributes. These Attributes are unique to God:
Eternal, Holy, Unchanging, Impassable, Infinite, All-powerful, Omnipresent, All-Wise, All-Knowing, Self-Existent, Self-Sufficient, Sovereign, and Immaterial.
What they could not bear to hear was the “message” of Baha’u’llah, the unity of mankind, etc. Clearly, humanity was not ready to hear such a message that back in the days of Christ. They are even having a difficult time hearing it now.
John 10:16 And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
Here Jesus is referring to His Second Coming, when all the religions would be gathered together and become one religion. As the return of the Christ Spirit Jesus promised to send from the Father, Baha’u’llah came to gather everyone into ONE religion, the Religion of the One God who created the universe.
Just as Christ held back some of what He knew back in His day, Baha’u’llah held back some of what He knew in this day because we are not capable of comprehending it yet...
“Oh, would that the world could believe Me! Were all the things that lie enshrined within the heart of Bahá, and which the Lord, His God, the Lord of all names, hath taught Him, to be unveiled to mankind, every man on earth would be dumbfounded.......
Of these truths some can be disclosed only to the extent of the capacity of the repositories of the light of Our knowledge, and the recipients of Our hidden grace.” Gleanings From the Writings of Bahá’u’lláh, p. 176
Baha’u’llah said that God cannot incarnate His Essence and reveal it to man. That means that the fullness of God can never be revealed to man, that we can never see it.
“Know thou of a certainty that the Unseen can in no wise incarnate His Essence and reveal it unto men. He is, and hath ever been, immensely exalted beyond all that can either be recounted or perceived.” Gleanings From the Writings of Bahá’u’lláh, p. 49
Referring to God as the Essence of all created things Baha’u’llah disclaims any direct relationship with God. He also says that every way is barred to the comprehension of the Manifestation of God, which is why we do not understand the nature of Baha’u’llah.
“Nay, forbid it, O my God, that I should have uttered such words as must of necessity imply the existence of any direct relationship between the Pen of Thy Revelation and the essence of all created things. Far, far are They Who are related to Thee above the conception of such relationship! All comparisons and likenesses fail to do justice to the Tree of Thy Revelation, and every way is barred to the comprehension of the Manifestation of Thy Self and the Day Spring of Thy Beauty.” Gleanings From the Writings of Bahá’u’lláh, p. 4
What no man could bear was that God was communicating with Baha’u’llah, working through Him, which is why every limb of His body was set afire by the power of the Holy Spirit.