Every body were muslims starting from Adam and Eve.... for example: Till Abraham (prophet Ibrahim alisalam) Jews were muslims and similarly till Jesus Christ (Esa Alaisalam) there were no christians.
All the muslims believe in the book of Jesus and book of Moses and in the book of David (Dawood Alisalam).
Based on my understanding (Dr. Zakir Naiks lectures) Muslims should not disrespect Rama, Krishna or Buddha).
