"Please give a single example of a rap artiste having good knowledge of Indian music as well."
Panjabi MC.
Other well known artists known to have promoted rap music (though not technically rappers themselves) include Talvin Singh, Ravaliya, Dave Sharma. Plenty other lesser known musical artists out there if you search hard enough.
"where is the pressing need to go gaga over something alien as rap music." If you are referring to the art of "rapping" (as I do not understand your "rap music" terminology), I can answer by simply stating that it is possibly one of the most powerful forms of vocal expression which can be just as effective as singing WHEN executed properly.
"As far as my knowledge of rap music is concerned, sorry to say that it has failed to make an impression on me exposed to Indian music from time immemorial."
You keep emphasizing rap music but I am not exactly sure what rap music is! I am referring not to what you term as "rap music" but to the art of vocally expressing oneself by rhythmical intonations ie rapping.
"alien as rap music."
Well then it's about as alien as Qawwali would have been back at around I think the 8th century. Qawwali had its original roots in Persia and so that would mean that prior to the time of its introduction to India it also would have been deemed as alien music. The same also applies to ghazals.
" By the way he is the only contestant who has attempted to sing rap which can't be said of the other lot"
But my point here is not that he has attempted it, but that he has performed it at a very poor level which is somewhat surprising given his mastery of the classical music as pointed out by the previous commenter. Maybe, his mastery of the classical music just simply isn't enough !!