Social class is only a concept and does not exist in the real world.
Operating under a bourgeois definition of class this would be true, yes. However, it is not true when looking at class from a Marxist perspective. Marxism is scientific and looks at the patterns of objective relations. There are certain objective elements called the means of production. They produce certain objects called products. All people in society somehow consume these products (or they die). These products are transferred to these people in ways that are objectively observable. And it is this relationship (between people and the means of production) that defines Marxist class analysis. It is not a social construct but a scientific view of society.
"The Communists disdain to conceal their views and aims. They openly declare that their ends can be attained only by the forcible overthrow of all existing social conditions. Let the ruling classes tremble at a Communistic revolution. The proletarians have nothing to lose but their chains. They have a world to win.
Workers of the World Unite!" -Karl Marx
"The dictatorship of the proletariat, i.e., the organization of the vanguard of the oppressed as the ruling class for the purpose of suppressing the oppressors, cannot result merely in an expansion of democracy. Simultaneously with an immense expansion of democracy, which for the first time becomes democracy for the poor, democracy for the people, and not democracy for the money-bags, the dictatorship of the proletariat imposes a series of restrictions on the freedom of the oppressors, the exploiters, the capitalists. " -Vladimir Lenin
"The People's democratic dictatorship needs the leadership of the working class. For it is only the working class that is most far-sighted, most selfless and most thoroughly revolutionary. The entire history of revolution proves that without the leadership of the working class revolution fails and that with the leadership of the working class revolution triumphs." -Mao Zedong