I think he’s right that the culture wars are winding down… a sign that the Boomers (born 1943-1960) are no longer at the cutting edge of the national mood.
It is inaccurate, though, to say that Millennials (born 1982-200?) support gay marriage. The Pew Survey (gold standard in this area, IMO) says that 18-29 remain deadlocked on this question in 2009: 45% con, 43% pro at last count. What is true, of course, is that they are much more supportive of gay marriage than older generations. And that a clear majority do support “civil unions.”