That's what needs to be emphasised here against the 'multiculturalists'/cultural relativists.
Just as an aside about cultural relativism: I consider myself to be a "cultural relativist" but in a different way. I don't see any morality as objectively true. I see some elements of morality as being subjectively true in all cultures.
What I mean by cultural relativism is this (and I know this is different from other people's cultural relativism): I think all traditional systems of morality and religion are deeply corrupt. So it bothers me when people (usually christian or jewish people) talk about how aweful Islam is (not that it isn't) because that tacitly implies (or sometimes is just blatantly stated) that their system is better. That is what I (as a "cultural relativist") believe. They are all bad so saying one is worse doesn't make sense.
"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