SourSteezleEheath clearly has no experience using IS lenses for video or he would have noticed a difference, it's not hard to tell that it helps alot. So no, I don't think he should discourage people from buying some of my favorite lenses because they're IS.
Also, I personally have a good time shooting shoulder mount with my 70-200, I'm surprised you don't.
First, to address the comment above-
You cannot say there are plenty of IS lenses that DONT get distorted. IS is essentially shifting light rays as they enter your lens. You're adding one more variable to effect how that light hits your sensor. I am not saying it happens all the time, however, it can be a problem and when it does become an issue on THE shot you need, you'll be wishing you weren't using it.
For example, this is especially true when your camera is on a tripod with IS on and you are panning, where IS can actually increase blurring. Using IS on a tripod also runs the risk of feedback loop. This is where the lens senses it's own vibration from IS and and tries to correct it, moving the element around even though the camera is still, which creates motion in your objects that aren't there.
Also, simply put, IS decreases sharpness of a lens. IS is 'using one motion along one axis to counter motion on the opposite axis, which creates varying degrees of degradation.'
I am not saying IS doesn't help, especially for handheld work, by all means get an IS lens if you're doing a lot of handheld work. However, to preach that it is perfect and has no effect on image quality is very wrong information to give to somebody. You should know how the technology works so you know when it's working against you as well.
In addition, I don't have fun shooting shoulder mount with my 70-200 II because I don't own or often work with any lenses that have IS.