"This" (the imprisoning and killing of socialists) arises because of authoritarianism. It happens in (ostensibly) "left" countries like China and the USSR and "right" countries like Nazi Germany, Pinochet's Chile, and even the US.

There is nothing "impractical" about socialism, unless you are saying it is impractical for all people to share in decisions about how their money and time will be spent. That is all socialism is.