How would it "discredit" him?It makes more sense to discredit him as an individual as if he dies someone else just takes his place. If you discredit him he may loose all credibility and his information an asserations won't be taken seriously.
It's not about "his assertions".
He has no particular credibility as a person.
It's the fact that he gets hold of and releases actual documents.
It's not like everybody's just been taking his word for everything, because he's got such a sterling reputation.
I didn't even know, or particularly care, who he was.
When documents are leaked, I'm not worried about whether the person who leaked them has once been accused- or convicted- of sexual harassment.
I'm looking at the documents themselves to gauge their veracity.
When the pentagon and the US government themselves admit the documents are legitimate and valid, I'm certainly not going to be like, "Oh, but the guy who leaked them was once accused of sexual harassment. So I think I'll just forgive the government for whatever transgressions are exposed in these documents, no matter how incriminating they are."