You can argue that butter is much better for you than margarine, but smothering anything in butter is not good for you - everything in moderation.
Kinda going off topic a bit but...
Butter actually
is good for you. Particularly butter from grass fed cows.
Butter contains short and medium fat chains which are metabolized differently from other fats. Instead of being stored in the body like fats from carbohydrates, the butyric acid (which is what butter is named after) is burned by the body for quick energy instead.
Butter is rich with vitamins, can help promote colon health and stave off cancer. Plus a bunch of other positive benefits.
Fat is the body's preferred form of fuel. Secondary is glucose. When you consume carbs, it raises your insulin levels. Insulin is a hormone that causes you to store fat and burn glucose instead. If you are consuming BOTH fats and carbohydrates, then yes, putting fats on everything is not going to be good for you. But if you are limiting your carbohydrates and getting most of your daily allotment of calories from fats instead, then there's no reason to think that butter is going to be bad for you.
The thing is, most people tend to consume a LOT of carbs throughout the day, leading to fat storage.