Disable dragging if fits will prevent dragging if the content is fully visible.
In that video not all the content is visible.
However one other thing I noticed: you have very weird scales. It's generally a bad idea to use scales other than (1, 1, 1) with NGUI (not including widgets). It's an even worse idea to use non-uniform scales like you do in there. As a rule of thumb, if you select the UIRoot, hit ALT+SHIFT+P and something changes visibly, then you should reconsider what you're doing.