Argumentum ad baculum (Latin for "argument to the cudgel" or "appeal to the stick") is the fallacy committed when one makes an appeal to force to bring about the acceptance of a conclusion. One participates in argumentum ad baculum when one emphasizes the negative consequences of holding the contrary position, regardless of the contrary position's truth value — particularly when the argument-maker himself causes (or threatens to cause) those negative consequences. It is a special case of the appeal to consequences.
The Stanford Encyclopedia of Philosophy gives this example of argumentum ad baculum:
The phrase has also been used to describe the 1856 caning of Charles Sumner, an abolitionist Senator, by one of his pro-slavery opponents, Preston Brooks, on the floor of the United States Senate.
...that uncompromising Sumner whose eloquence exasperated a fiery Southerner into the employment of the argumentum ad baculum...