Baha’is calling Krishna a Manifestation of God are just giving their own opinion about it.
Jim I do not see it that way, as Krishna has been mentioned in enough detail by the Writings to safely use the term Manifestation of God. After all Baha'u'llah tells us they are one and the same Spirit and Baha'u'llah is the return of that Spirit of Krishna.
These are some of the quotes (I like the 2nd one, it mentions Atheists)
;
1) "An Indian said to Abdu'l-Bahá: 'My aim in life is to transmit as far as in me lies the message of Krishna to the world.'
Abdu'l-Bahá said: The
Message of Krishna is the message of love. All God's prophets have brought the message of love. None has ever thought that war and hate are good. Every one agrees in saying that love and kindness are best." Abdu'l-Baha : Paris Talks
2) "...The Jews await the Messiah, the Christians the return of Christ, the Moslems the Mahdi, the Buddhists the fifth Buddha, the Zoroastrians Shah Bahram, the Hindoos
the reincarnation of Krishna, and the
Atheists - a better social organization! Bahá'u'lláh represents all these, and thus destroys the rivalries and the enmities of the different religions; reconciles them in their primitive purity, and frees them from the corruption of dogmas and rites." Abdu'l-Baha : Tablets of Abdu'l-Baha Volume 1
3) "...He alone (Baha'u'llah) is meant by the prophecy attributed to Gautama Buddha Himself, that "a Buddha named Maitreye, the Buddha of universal fellowship" should, in the fullness of time, arise and reveal "His boundless glory." To Him the Bhagavad-Gita of the Hindus had referred as the "Most Great Spirit," the "Tenth Avatar," the
"Immaculate Manifestation of Krishna." Shoghi Effendi : God Passes By Part 1
Are you asking my opinion? In my opinion, if there is any such authority, it is certainly not any Baha’i or Baha’i institution. In any case, I don’t see that Baha’is have any privileged status in answering the question.
"Your question concerning Brahma and Krishna: such matters, as no reference occurs to them in the Teachings, are left for students of history and religion to resolve and clarify."
- Shoghi Effendi or on his behalf, April 14, 1941, to an individual Baha'i
With that quote, we do not know what was the question was, "Your question concerning Brahma and Krishna" and we do not know what were the "such matters", that "no reference occurs to them in the Teachings".
Edit: Jim I note a few replies were done as I wrote this up and covered most of this reply, it took a while, I got interrupted quite a few times...
Regards Tony