Seems that the truth is probably somewhere in the middle between the book and "we was a great dad." I am guessing that part of the motivation to "he was a great dad" was to protect his reputation and probably the value of his music, movie, image, etc rights of which I'm sure they all got a piece. Gary's book may or may not have been the truth and his recanting may have had to do with embracing the real truth or trying to make amends to the family and his father's memory.
I think for the most part people separate their 'love' of the artist and his art from the person. There are ugly rumors (or truths) regarding many artists out there. Back in the day much of these were swept under the rug as people were paid off by studios etc to not report drinking problems, drugs use, affairs, homosexuality, etc, Many of these things are now commonly ignored or blow over with the public or are complete non-issues and media coverage is so much more intense that almost everything eventually comes out.
Bing's issues (whatever they were) were more shocking because he had such a lily white image and they came from a close family member and he was an icon with a different generation. As I said we don't know the truth but, I'm guessing from the family history of alcoholism, divorce, depression, and suicide in his sons that there is something to these stories to what extent? Who knows? The bottom line is his work is what it is and those of us who enjoy it should do so regardless. The truth is artists, singers, actors, and geniuses are all humans and they all have their flaws or perceived flaws. It is best to enjoy the persona and their work and not dig too deep unless you are prepared to handle what you find.
If you are a fan of the cinema and are a homophobe it is best to avoid looking into your favorite stars' lives as many of them will leave you disappointed. Personally I don't care about that or many other issues when I watch, look at, read, or listen to their performances. I do have a few flaws that I can't ignore but, don't we all. Imagine how much poorer we'd be if we threw away all the art, music, writings, and movies produced by someone that doesn't meet some lofty standard.
I think that for the most part Bing is remembered fondly and rarely do I see these references and when I do they are a passing joke with little or no impact...