elprofesor
Pluri-editing poster
http://en.wikipedia.org/wiki/Double_negative#Two_or_more_negatives_resolving_to_a_negative
Sorry, but the first section of the phrase really bothered me.
His sentence is perfectly correct, he is using two negatives to form a positive. The "double negative" error comes when you are using more than one negative to intensify a negative, even though it doesn't work that way grammatically. That's actually what is explained in the link you provided.
Sorry for being nitpicky (and off-topic), but your correction bothered me.