Actually Billy Bishops war record holds up quite well ,when compared to his peers. The controversy started in 1982 when a film maker, using government funds, produced a "docu drama" entitled "The Kid that couldn't miss". The producer openly admitted that his intent from the outset was to produce an anti hero movie. Because it was very poorly researched ,containing many factual errors, the film lost what little creditability it had and was more or less forgotten , but oddly enough is still available from the national film board of Canada.
More recently{2002} a Canadian historical writer named Greenhous published a book titled "The Making of Billy Bishop". This attack on Bishops credibility was more insidious , but just as unfounded.
A good place to read up on the controversy is
William "Billy" Bishop
Read it over if you have the time and make your own conclusions. The sections cocerning his being awarded the VC are the most enlightening as that is the central area of the alleged conspiracy/controversy.
Slaterat