No, you may not omit the do.
A question headed by a Wh- interrogative (who, whom, whose, what, which, where, when, why, how, and a few others) must have a finite verb in the second position†; and that verb must be either a form of be or an auxiliary verb.
He is right. Why is he right? ... the finite verb IS is a form of BE
You must fight. Why must you fight? ... the finite verb MUST is a modal auxiliary
But if the finite verb in the clause is not one of these, then it must be replaced with a do construction (this is called 'DO-support').
You fight. *Why fight you? ... wrong: FIGHT is not an auxiliary
*Why you fight? ... wrong: there is no verb in second place
Why do you fight? ... right: DO is an auxiliary in second place.
A tricky piece is that do and have (and a few other verbs) may act as either an auxiliary or as an ordinary lexical verb. You must be careful to employ do in the second case:
They do wrong. *Why do they wrong? ... wrong: DO here is not an auxiliary
Why do they do wrong? ... right: the first DO is an auxiliary
He has a car. *Where has he a car? ... wrong: HAS here is not an auxiliary (but
this was at one time acceptable)
Where does he have a car? . right: DO-support provides the auxiliary
† Second must sometimes be loosely interpreted with which, what and whose; if used as adjectives these are followed by the NP they modify, as in What courses are you taking?
* before an utterance indicates that it is not ordinarily acceptable