Rajesh, that was one reasonable thought among a bunch of gibberish nonsense and abuses. Like you, I too was in a christian school (because that was the best in our city), remember to have also read biblical history and never once thought of becoming a christian (though many here seem to assume so based on the name).
Every religion today has it's share of bigots and practices that seem to defy & contradict their own core preachings and morals.
The tragedy is they run the show.
So the best a person can do is point them and move on with your more important things of life - family & work.
Seven Maniacs, the "Khan" thingy need not be hypothetical. It could happen. A certain Sarod Maestro, the nation reveres, is married to a Hindu Lady (perhaps a brahmin). According to our tantri, they only look at matriarchal lineage, which means their children would not invite a purification. My opinion (as one decent practicing hindu), allow everyone who wishes to visit and maintain the decorum of the place.
For, A Late Bismillah Khan & Abdul Kalam are devotees of Goddess Saraswathi and are people of great distinction to be cherished for their contributions. It would be a sad day for the nation & hindu religion to see them hurt by overzealous bigots.