Why does he say to Kyra Sedgwick's character...

... after asked about the details - "What are you sick, do you get off on it?" - does Walter really believe that women, or some of them, alone can be "sick" and simply "get off" on hearing such stories as opposed to simply maybe wanting to find out more about the nature of his offenses and then decide if to stay with him, leave him, help him etc?

Didn't he perhaps think in his mind, given especially how bad he felt it, that maybe perhaps only men like him can either be capable of such offenses let alone derive any even theoretical enjoyment out of it? Or did he know or suspect, perhaps, something else - as much as he does know about the common side though?