Why was Starship Troopers called a fascist book?

"Starship Troopers," written by Robert A. Heinlein, is often labeled a fascist book due to its depiction of a militaristic society where citizenship and political rights are granted only to those who serve in the military. The novel presents a worldview that prioritizes duty, sacrifice, and the collective good over individual rights, leading some critics to argue that it promotes authoritarian values. Additionally, its portrayal of war and the glorification of military service can be interpreted as endorsing a fascist ideology. However, supporters argue that Heinlein's work is a critique of society rather than an endorsement of fascism.