I found nothing saying that he said Mia Farrow brainwashed her children to lie about this. That doesn't mean he did not say it.
I did find articles when he spoke out at the time of the controversy supporting Mia Farrow and Dylan and attacking Woody Allen.
http://www.people.com/people/archive/article/0,,20108514,00.html
http://articles.baltimoresun.com/1993-03-24/news/1993083105_1_farrow-woody-allen-moses
There have been witnesses who spoke of Woody Allen's inappropriate behavior towards Dylan. Dylan's recent letter is consistent with these accounts.
The ironic thing is that most of Woody Allen's best films were the ones he made with Mia Farrow. Broadway Danny Rose, The Purple Rose of Cairo, Hannah and her Sisters, Radio Days, Crimes and Misdemeanors, Husbands and Wives, etc. And other than Rosemary's Baby, which was directed by Roman Polanski, they were Mia Farrow's best films. The same Roman Polanski convicted of drugging and raping a 13 year old girl. The same Roman Polanski who Mia Farrow has defended.
I always liked Woody Allen's films. I remember seeing Annie Hall with my girlfriend of the time and us recounting scene after scene laughing when it was over. I have seen Midnight in Paris several times on cable and like the photography at the beginning and the references.
I don't pretend to know with certainty what happened. But the evidence suggests that Dylan is telling the truth.
My biggest problem with Farrow is that she has supported and continues to support Roman Polanski. I guess in her eyes it’s OK to molest some children but not hers.
Here it the article that contains the info about Moses.
The second article is about the Nanny who was in the home at the time of the alleged molestation. She claims it couldn’t have happened and that Moses backed up her claim.
http://www.thedailybeast.com/articles/2014/01/27/the-woody-allen-allegations-not-so-fast.html
http://articles.latimes.com/1993-02-02/news/mn-952_1_woody-allen