Throughout the history there have been conversions by force, bribes and other illegal and immoral ways. In today's world of multi-ethnic, multi-religious and multi-linguistic societies, there is a need for a qualitative conversion of people ie. from ill will to good will, hatred to compassion, extremity to equanimity, impatience to patience and from ignorance to wisdom, but not the conversions from one organized religion to another organized religion. Just the increase in number of particular religion will not help humanity in any way on the other hand it may lead to religious arrogance and spiritual ignorance in the name of majority.
 
The wrong view that their own caste, race and religion is superior and that the increase in number of their particular caste, race and religion would guarantee them peace and prosperity has lead to economic, social and spiritual deterioration of human society. In Parabhava sutta the Buddha explaining one of the many causes for ruining of man says:
 
Jatitthaddho, dhanatthaddho,  Obdurate about race, obdurate about wealth  
Gottatthaddho ca yo naro,        That man, also obdurate about tribe,          
Sannatim atimanneti,                 Despises his own relatives (humans),         
Tam parabhavato mukham.       That is the cause (of ruin) of ruining man. 
 
Further, the Buddhist view towards conversion can be understood clearly from what Buddha said to Nigrodha as follows:
 
I teach dhamma, Nigrodha, not wishing to convert pupils, not wishing to make you fall from your religious studies, not wishing to make you give up your mode of living, not to establish you in things accepted by you and your teacher as evil and unwholesome, or to make you give up things regarded by you and your teacher as good and wholesome. NOT SO.
 
But, Nigrodha, there are evil and unwholesome things not put away, things that have to do with defilements..... It is for rejection of these things that I teach the dhamma: walking according to which, things concerned with defilements shall be put away, and wholesome things that make for purity shall be brought to increase, and one may attain, here and now, the realization of full and abounding insight". (Udumbarika Sihanada sutta D.N.25).
 
On another occasion Upali, a fervent follower of Nigantha nathaputta, the Jain, visited the Buddha, mindfully listened to the Dhamma and having gained confidence expressed his willingness to become a follower of the Buddha. Nevertheless the Master told upali to make thorough investigation of the truth and not to be in a hurry. Thus even after Buddha, his followers throughout the history never tried to bribe, cajole or coerce people to their fold nor do the Buddha’s teachings ever interfere with another man’s freedom of thought; for freedom of thought is the human right of every individual. Compulsion in any form is inhuman and goes directly against the spirit of any humane religion.
 
Thus human welfare and happiness should be the priority than just conversion by unethical means to any one particular religion. Because Man is not made for religion but religion is for man.
 
Different societies, religions and sects have different ways of worship, different places of worship, different rites and rituals, different festivals, different vows and fasting days. Their philosophical beliefs are different. Thus different religions and sects originate and flourish on the basis of these differences. But the wholesome qualities of love compassion, patience and wisdom is universal and is morally accepted by all religions, sects and societies. While continuing to maintain their distinct sectarian features it is the universal wholesome qualities of love, compassion and wisdom that unites all religions, sects and societies. The basic problem of humans is the defilement of greed, hatred and delusion. Therefore any path or religion which can lead to non-defilement and thus establish us on the path of non-greed, non-hatred and non-delusion is the most right, divine and humane religion.
 
Therefore the human interest should be in Dhamma-The truth, the teaching of the All Enlightened ones. Which inspires us to walk on the non-sectarian, universal Noble eight-fold path. The path which leads from misery to happiness, defilement to purity, bondage to liberation, & ignorance to Enlightenment.
 
Therefore there is no need to rush for conversion of people from one religion to another religion but surely one should work for the qualitative conversion as already mentioned above. 
 
Thus let all of us wish that in this world of various diversities may there be unity of humanity with wisdom, peace and prosperity.
 
   
It is Universal Nature's quality
To have Unity in diversity
To understand this one need not go to some University
But should develop the heart of sensitivity
And must have love for humanity.
This path to humans unity
Is Wisdom, Concentration & Morality.