In 1984 why doesn’t the Party just shoot or hang dissidents when it captures them?

The Party wants to create “true believers.” In Goldstein’s treatise, he explains that past dictatorships and other oppressive regimes made the mistake of publicly executing people while the dissidents still held to their unorthodox beliefs. All this did was make the executed person a martyr and therefore create more rebels. For a totalitarian regime to hold onto power, they must brainwash the dissident so thoroughly that the rebellious person starts to believe in the dogma of the ruling party or group. Failing that, they must find a way to reduce the person to a shell of a human being so that the person has no impact on the world or desire to change it. In this way there are no martyrs; there are only true believers. The opposing voices have been silenced.