On June 6, in East Wenatchee, Oregon Waterville, Washington, a 17-year-old girl attacked her 21-year-old brother with a "knife-edged barbecue spatula" after the two argued over how to make macaroni and cheese.
The girl told police that she was making the dish when her brother asked her if she was using butter. According to the police report, the two then "began to argue over the difference [between] real butter [and] margarine." (The report is not entirely clear as to who advocated for which substance.) The argument escalated, and shortly thereafter the brother called police to say that his sister had just tried to cut his neck with the sharp, serrated edge of the spatula. She was charged with assault on June 10.
I think the right answer here is that you should always use butter, unless there is someone else in the room who disagrees very strongly and is holding something sharp.
Note: Most reports on this story place the event in "East Wenatchee," but it actually seems to have happened in Waterville, a small town about ten miles northeast of Wenatchee (apparently small enough that the brother called police in East Wenatchee, which is where that detail came from). An alert reader (from Washington) pointed out that both towns are in Washington, not Oregon, which was my mistake.
I stand by my (conditional) opinion about butter vs. margarine, though.