Tough anti-terrorism policies are often defended by focusing on a fixed minority of dangerous people who prefer violent outcomes, and arguing that toughness reduces the risk of terrorism from this group. This reasoning implicitly assumes that tough policies do not increase the group of ‘potential terrorists’, i.e. of people with violent preferences. Preferences and their level of violence are treated as stable, exogenously fixed features. To avoid this unrealistic assumption, I formulate a model in which policies can ‘brutalise’ or ‘appease’ someone’s personality, i.e. his preferences. This follows the endogenous preferences approach, popular elsewhere in political science and economics. I formally decompose the effect of toughness into a (desirable) deterrence effect and an (undesirable) provocation effect. Whether toughness is overall efficient depends on which effect overweighs. I show that neglecting provocation typically leads to toughness exaggeration. This suggests that some tough anti-terrorism policies observable in the present and past can be explained by a neglect of provocation.