A common way that sexual harassers explain their behavior is

The common way they do to explain their behavior is by saying that he or she only flirting with the victim.

A lot of sexual harassers do not even aware that they make their victim feels harassed. in their mind, the victims are attracted to them and they're just flirting with the victims in order to get their attention. Another way they explain their behavior is by saying that the victim is the one that make the first move by doing provocative gesture or wearing provocative outfits

As the previous responder has noted - it is quite common for a sexual harasser to misinterpret (or at least try to convince the judge) the signals he or she was receiving from him or her. This is a common lie but can also be a fact if the person has some deficits in social functioning; which isn't necessarily that uncommon in such perpetrators.