The man-made object responsible for the most deaths worldwide is the tobacco cigarette. It isn't even close.
Tobacco kills 443,000 Americans a year and 5 million people a year worldwide. This is more than the total number of people killed by cars and firearms combined. Cars kill about 32,000 Americans each year and 1.3 million people worldwide, while firearms kill about 32,000 Americans each year and "several hundred thousand" people worldwide.
100 million people were killed by tobacco in the 20th century. This is more than the death toll from World War 1 (17 million) and World War 2 (50 to 70 million) combined.
From a strictly utilitarian perspective, would there be anything to be gained by, say, starting a campaign of assassination against executives of tobacco companies?
could you point me to the heuristics that say that violence is always a bad strategy? I have a strong gut feeling that they're right, but I'd really like to see them in a formalized or semi-formalized fashion :-)
There's nothing to point at; that's the whole heuristic. While there are lots of good arguments for violence being bad in general and in specifics, the only thing a heuristic requires is that when asking "is violence a good strategy here?" the answer is almost always "nope". Which it is, but for a slightly different mix of reasons every time you ask it.