Trujillo's government is a dictatorship. If anyone does anything at all that displeases him or his cronies, they can do whatever they like: jail, physical violence, death. One example of their brutality can be found in Ch 6, p84 (*my edition, your pg # may vary). Those who resist the government "disappear" (are killed). The "Resistance" which Lio and Minerva are involved in, want to overthrow this brutal leader and establish a democracy.
Minerva is motivated not only by the crimes against men in her country, but also the exploitation of women. When she is sent away to school, she watches in horror as her good friend Lina Lovaton, is taken away to Trujillo's compound to become a concubine (sex slave.) (CH 2, 20).
*Furthermore, like other dictators around the world (remember the huge paintings and statues of Saddam Hussein ?) Trujillo insists on being praised by everyone at all times. This is evident when Minerva has to give a speech praising "El Jefe" (Trujillo). It doesn't go as Trujillo expects. The scene at the end of Ch 2 is quite scary with Minerva and her friend Sinita disobeying the official "script" for the performance (Ch 2, 28-29)
These are just a few of the many examples of brutality. They are especially prevalent in Ch 2 and throughout Part III.