I was amazed at the number of commentaries on this particular study that can be found on the internet. There are numerous criticisms of the factual reliability of penis size claims as disclosed by the Kinsey study. Here is a typical critique:
'...the study's fatal flaw, if I may, is its reliance on self-reported data. The straight and gay men in the study were asked to measure themselves and report back to creepy Dr. Kinsey, so odds are good that many men, straight and gay, lied, telling researchers what they, the subjects of the study, wanted to believe -- i.e. that their cocks were huge. I would knock an inch off both averages just to be on the safe side, bringing the average -- average, mind you -- gay cock down to 5.46 inches, and the average straight cock down to 5.14 inches; numbers which jibe with my own observations in the field.' (Dan Savage)
Bottom line, we just have more size queens.