Hinduism has the best philosophy. But for common man,the practices represent religion. And there are several age-old costumes by which the common Hindu practices religion. One of the most important customs is entering temple to offer prayers. (There are no lectures by priests in these daily prayers). If christians or muslims enter shoulder to shoulder with Hindus just to gawk, it will make a mockery of the whole process.
Every christian, by the very philosophy of their religion, has an inborn desire to spread christianity by hook or crook. But dont forget that Hinduism survived centuries of genocide and conversion by sword by muslims and conversion by authority, misinformation ,exploitation of poverty, disease and disasters by christians and their missionaries.
Why Yesudas want to enter Guruvayoor temple? He is an ardent christian. For Christians or muslims there is only one god, their own.Experience has taught him that he can exploit the gullible Hindus for fame and wealth. Hence the show at Sabarimala. Let him first convert to Hinduism. For him to publicly express the desire to enter Guruvayoor temple, is a slap at every Hindu's face.