Maybe there's an assumption that this means commercially prepared fried foods, which may use soybean oils that aren't cleaned/changed regularly?
http://www.livestrong.com/article/504208-how-many-calories-d...
Makes sense. I'm not sure if you were implying this, but both ends[1] of the diet spectrum seem to decry "industrial" fry oils which are hydrogenated and thus full of the undesirable trans fatty acids.
Even if they were cleaned or changed regularly, they would still contain those undesirable components.
[1] By both ends, I mean the low-fat, vegetarian-style end (Ornish, etc) as well as the high-protein, high-fat style (Atkins, Mediterranean, Paleo, etc).