1: I should not respect you.
2: Should I not respect you?
3: Shouldn't I respect you?
The sentences 2 and 3 are the interrogatives made from the sentence 1. The sentence 3 is much more common than sentence 2. In grammar, a clause that is in the interrogative has its subject following do, be, have, or a modal verb. That means sentence 2 is grammatically correct. If that's the case, then sentence 3 is grammatically incorrect. If it is, then why is it used so frequently? Perhaps, it's just idiomatic.