I don't want to. You could stop trying to avoid the topic at hand, but I understand that you find it very hard to ever admit to being wrong or making a mistake. You should try it some time, it actually feels good.
Yes you are. If the allegation is false, then you're actually the one who is victim-blaming right now. But that's a possibility that you refuse to consider, because you seem to think it's sexist to suspect one individual woman of making a false accusation. If it was a man filing a lawsuit that he got beat up or robbed 25 years ago at that same party, I would be equally skeptical of his claims.