Saying that Krishna is a "manifestation of God" and that he had a "message of love" does not mean very much. Many special people (Maharishi's) were in their own way a special "manifestation of God" and taught (universal) love in their teachings.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
However saying that Bahaullah is the "reincarnation or immaculate manifestation of Krishna says a lot about the Bahai faith. They really seem to have little idea about who Lord Krishna was or they would never say such things. Of course no Hindu even would ever say that Krishna would/will reincarnate. If you accept (which I don't) that Krishna was an incarnation or avatar of Vishnu, then you would expect a new avatar of Vishnu and not a reincarnation of Krishna. Deities do not reincarnate, they are no ordinary beings.