The question this axis asks
Should people be expected to adopt the common culture, or should a society welcome and support different cultures?
This axis is about integration, language, shared national culture and the place of minority traditions. It does not ask how many people should immigrate, which is a separate policy question, but what a society should expect from, and offer to, those who live in it.
People on the Assimilationist side usually argue that a shared culture and language create trust and equal opportunity. People on the Multiculturalist side usually argue that diversity enriches a society and that people should not have to give up their heritage to belong.