Socialist states end up in a dictatorship of the proletariat, usually in some form of democratic centralism.

Capitalist states end up in a dictatorship of the bourgeoisie, otherwise known as bourgeois democracy or oligarchy, with occasional lapses into fascism.

i assume you realise capitalism isn't a defense against dictatorship either? almost every country in the world currently is capitalist, and yet, half of them are a dictatorship, or nearing it (how long til freedom country officially stops being free? there's still some resistance)
and also that the usa did everything in their power to curb the spread of communism? multiple democratically elected somewhat socialist leaders were killed or at least deposed, to place money friendly tyrants instead, the ones that survived, were like castro in cuba, because they were extremely careful, to the point of paranoia, or they were too big to tackle, like the soviets and china. not to mention they participated and participate even more nowadays in (state) capitalism