There is sooo much more to the wind turbine issue, he's right though, there is a shadow drag/resistance.
There is also a load resistance factor, even though these things are turning, it can be an illusion, the more demand/load placed on a turbine, the more wind is needed.
Take a bicycle and the person peddling along exerting little effort to maintain 7 MPH, but a hill comes along, he has to increase output considerably to maintain his speed, a wind turbine works the same way, if demand is light (plenty of current being generated by other sources) the turbine produces fine, but when demand is placed on it, it needs a lot more wind to keep it moving.
Point is, you can't turn up the wind when needed, and if demand is light, you don't need them.
In other words, it's all freakin feel good hype!
Did I make that clear, or do I need to expand on it?
It's 2:30 am and I'm not real alert yet.