Pachy,
What is it that you hear when he is brushing off your feelings? Are you hearing, 'Look, I don't want to think (deal with) about the possibility that you did this horrible thing. So, since you really can't remember either way, lets just assume that you didn't actually do it."-- What you don't know can't hurt you kind of thing?

Would your rather have him assume that you DID do something bad and work from this perspective? I might like this approach better than simply being placated with 'you didn't do something bad, so let it go.' At least that way I would know that my T was still willing to work with me even though I was a "bad" person. I frequently think that I my T knows what I am really thinking or feeling, she will think I am a total jerk and would kick me out of therapy. If I admit to feeling guilty about something, I would not response well if she just said, "Ah, you didn't do that." I would much rather hear, Wow, that's pretty serious what makes you think you did X? Or, OK let's ASSUME you in fact did X, can you do anything about it now to fix or reduce your guilt? At least doing either of these would tell me that my T is still willing to work with me even if I did something I perceive as really bad.