I believe that Marnie Hair, a Dakota neighbor and mom of Sean's playmate, Kaitlin, talks about the 1961 Hamburg Stuart incident in the Goldman book. She claims to have heard the story from Yoko, when they were hangin' buddies.
Goldman also cited Jesse Ed Davis as a source for the Hamburg sailor mugging
story that Pete Best also has spoken of.http://www.nybooks.com/articles/4122
This stuff is all so sordid. Let's just say that John had a really dark side (like Sinatra.)
I've got to say that John was my fave Beatle. I especially admire that he tried to face up to his demons (understand why he was so angry and deal with it), finally, by doing psychotherapy with Art Janov and trying to change his ways.