well, i think sexual charges IN CASES LIKE THIS should ABSOLUTELY look into things like that--they're entirely different from assault charges.
without corroboration, it's equally likely that Kobe Bryant and his accuser are telling the truth. both the prosecution and the defence have to show that their side is more trustworthy.
if you applied the standards of proof for a case like regular assault or theft to a rape case, you would have virtually NO convictions, because so much of it can come down to one person's word against another, which is not adequate. so i support the delving into both peoples' backgrounds to a very large degree, because it enables legitimate convictions of rapists. otherwise, if you're being fair, more than ninety percent of rapists would go free, and that is not acceptable; or, if you're unfair, an accused rapist would be convicted without his guilt being adequately proven, which is also not acceptable.
invasive background stuff enables justice against rapists. disallowing it stops justice against rapists.