According to you there is no discrimination in India. Are you claiming that majority of the lower ranked officers are not dalits or not muslims? You may be right that he is too high ranked to be a muslim/dalit, but I am just assuming. And my observation is that Havildar is not that high of a rank to him not be a muslim or a dalit.
You don't need to be Einstein to make this kind of assumption. Majority of the lower ranked officers from 3rd world countries are often from poor background, those from better backgrounds might enlist as lower ranks but they get promoted fast. Sure, even in Pakistan majority of lower ranked officers are from poor background(I repeat I said majority not all). Since majority of Indian poor population is either dalit or muslim
one can assume that this particular guy is a dalit.