I agree. I will report this and I'm sure the only choice will be to delete the sentence.
Edit: Turns out they can leave the sentence but disable the audio.
Update 3/29/19: Recently Duolingo has added tools to allow contributors to record their own audio for the sentences. I'm now hearing a woman's voice (Brazilian, I believe) and she is now clearly NOT saying "ni ne".
I don't know what to say. Are you hearing the voice (I call her the "second woman") where she says "Cxu"... with a slight pause ... and then the rest of the sentence?
I hear: cxu .. ni estas ... bonaj ... patroj.
If you're hearing "ne" - try a different device, try different speakers or headphones, and if you're still hearing it, consider it ear training.
I can clearly hear "Cxu ni ne estas bonaj patroj". I don't have the Brazilian woman speaking in this sentence like mentioned in other comments, rather it's a male voice. 31/03/19