All I know is that I trust my father's (sports doctor and nutritionist) opinion, because he knows a hell of a lot more than I do about biochemistry. He has stated over and over again, that he believes margarine to be one of the worst things on the planet someone can consume.
I think butter got a bad rep in the same way egg yolks did. People date themselves when they make these antiquated and disproven arguments.
I agree butter may not be the best choice, and possibly should be avoided entirely, but I would tell anyone, even the most out of shape person to choose it over butter any day.
So you are saying to choose butter over marg, right?