"Character slamming someone who claims harassment is beyond inappropriate."

It's actually a significant part of our rules of evidence, in both civil and criminal proceedings.  In a trial, character evidence may be offered to impeach or strengthen the credibility of a witness, subject to certain limitations.

In the context of harassment, sexual assault, etc., you can't introduce character evidence about past sexual conduct (i.e., she slept around so she couldn't have been harassed) - that would certainly be beyond inappropriate, but that is not what is happening here.  You are very much allowed to introduce character evidence that is relevant to evaluating whether a witness is generally honest.