So when it comes to religion, it is not unity in diversity, but to get rid of the diversity?
As for Bahai's, they are to socialize with the followers of all Religions. I quote Bahaullah:
"O people! Consort with the followers of all religions in a spirit of friendliness and fellowship."
And again in another Tablet Bahaullah wrote:
"Consort with all men, O people of Bahá, in a spirit of friendliness and fellowship. If ye be aware of a certain truth, if ye possess a jewel, of which others are deprived, share it with them in a language of utmost kindliness and good-will. If it be accepted, if it fulfil its purpose, your object is attained. If any one should refuse it, leave him unto himself, and beseech God to guide him. Beware lest ye deal unkindly with him. A kindly tongue is the lodestone of the hearts of men. It is the bread of the spirit, it clotheth the words with meaning, it is the fountain of the light of wisdom and understanding…."
So, Bahai must and are supposed to be able to socialize with followers of Religions.
However, there are many non-Bahais, who are in conflict with the followers of other sects and religions, and for centuries are killing each other.
Others may not be explicitly engaged in killing of other religions, but treat other religions as strangers, or unequally, due to the hidden fanaticism in their heart. They have caused religion to be the cause of war and disunity, and injustice.
For them, Unity is the solution Bahaullah ordians. Thus, Bahaullah who identified that one major cause of conflict has been religious fanatiism, has wished, that diversity of religion be ceased. In the site of Bahaullah, Truth is One. Diversity of religion does not work, because they have not been able to see all people with the eye of unity.
Farther Abdulbaha explained:
"His Holiness Bahá’u’lláh has announced that the foundation of all the religions of God is one; that oneness is truth and truth is oneness which does not admit of plurality. This teaching is new and specialized to this Manifestation.
He sets forth a new principle for this day in the announcement that religion must be the cause of unity, harmony and agreement among mankind. If it be the cause of discord and hostility, if it leads to separation and creates conflict, the absence of religion would be preferable in the world."