I apologize for being so pedantic but I must again qualify that statement.
There are acute changes on insulin sensitivity and in those somewhat insulin independent glucose uptake mechanisms that are short term and mostly fade by 48 hours after exercise. And there are long term training effects (pdf) that prevent insulin resistance from occuring.
Beyond the biochemical mechanisms discussed in that review are the probable effects of the changes in body composition that regular exercise produces (decrease in central obesity and increase in fat-free mass) and the anti-inflamatory aspects. (Although to be precise at this point we cannot say which is chicken and which is egg, just that the changes are correlated.)
Such statements do not contradict your claim; they merely expand it. Increasing sensitivity and preventing resistance are not exactly the same thing. Treating established resistance requires ongoing regular exercise and if stopped the effect stops. Preventing resistance from developing or progressing OTOH is achieved with regular exercise and the resistance thus prevented does not suddenly occur upon cessation of exercise for a few days or weeks.