Gould is an engaging writer. However, he is also very prone to bending facts to suit his predestined conclusion, as I quickly realized while reading his Mismeasure of Man.
He is, quite simply, an avid partisan, and he makes good money at it. As such, his conclusions are not to be trusted at face value.
I don't limit this skepticism to Gould, BTW, he just happens to be the person we're talking about.