You're safe with your butter spray, Ski.
The main problem was trans fats, which have been removed from most, if not all, margarine products.
Butter contains cholesterol, which would explain why your cardiac team recommend alternatives.
As for being one molecule removed from plastic, consider this. Ozone is different from oxygen by the addition of one oxygen atom. Molecular oxygen is necessary to life, while ozone is poisonous at the same concentration as carbon monoxide. The human body is mostly water, but we don't need to stand in a bucket to prevent us leaking.
That said, health is a life long process, and it doesn't hurt at all to consider what the effects might be of a bit of convenience. Margarine, as originally formulated, WAS dodgy, but fortunately, the war on trans fats have reduced the risks.