I think (1) the relationship with Soon-Yi is creepy even if she wasn't his stepdaughter and (2) I have no way of deciding the truth of Dylan Farrow's accusations, and neither does anyone else.
With Dylan Farrow, it's on par with LRC's doping poll. No one has any basis for saying one way or the other whether 95% of the people in the poll doped and it's pure speculation. With a couple of people like Mary Decker, there's at least evidence that can be debated, but it's mostly speculation.
You might as well ask if you believe in alien life forms. In the absence of real evidence, you can create whatever make-weight arguments you want.
With Woody Allen films, I like the early, funny ones.