Proof?? Again you should go to a british or american consulate with an avowed intention of converting the pagan christians and then see how fast they throw you out. the number of hindu priests that are allowed is a small trckle and these priests are usually meant for conducting rites in temples
The reason why such visas may be refused is due to migration reasons..the chance of the priest running away from his sponsor and joining the illegal economic migrant population is pretty high.
There are all sorts of restrictions for people from Third world nations to visit the USA..most restrictions are to prevent economic migrants.
Most Christians dont really bother about such priests and dont want to restrict their religous freedom. Do you really think that the US or British state dept authorities are concerned about protecting Christian valuees? Are you for real? Do you even reside in the US? Just browse the any number of topics in FR that deal with the State dept and see what they stand for.