To understand this, you need to comprehend what Marx meant by the idea of a “class dictatorship”. Bourgeois democracy (i.e. liberal democracy) was considered by Marx to be the “dictatorship of the bourgeoisie”. If the system is designed to favour the interests of a particular class, it is a de facto class dictatorship, even if it operates on the basis of an internal democracy. Marx expected that the dictatorship of the proletariat would be a multi-party democracy, however, it would exclude parties that represented bourgeois interests and institute measures aimed at eliminating all social classes and creating an egalitarian, classless society.