You are absolutely right in saying when it comes to short term gains,but the people who are engaged in conversion and who get political benefits out of conversion,they do keeping in mind long term gains,that is making India a christain country by hook or by crook.The hindus who vote them do so by seeing short term gains which parties like congrees dish out,but what they fail to see is their very servival is threated by doing so,as in ORISSA case.
Christains in India suport conversion,thinking it is good India becomes christain majority,but what they fail to take notice is the intolerance fed in the minds of new convert children their systematic brainwashing.Today they have money and political power,tommorow it will be some one else.Today they feel hindus gettig converted to any denomination of christainity is good,but tommorow they will repent the compitition and hatred generated by rival groups trying to steel each others flock. Unlike Other countries this difference and haterde between different christain groups will become intense and bloody,the hatred between catholic and protestants in India though not known for hindus to see,is very visible for insiders.
