Your friends might be thinking of conformism (orthodoxy in thoughts and belief, pliancy to assimilate), which is the extreme version of collectivism. As far as I know, Marx never said collectivism must completely replace individualism. They both must co-exist, because either of them alone will lead to its extreme version. Individualism alone always leads to egoism (when an individual prioritizes his own interests and desires at the expense of his social group). Marxism doesn't impose selflessness, since individualism is in some circumstances a necessary form of the self-assertion of individuals, but it demands balance. Without collectivism, the extreme form of individualism will rear its ugly head and push people to treat others as expendable and exploitable, which violates individual liberties, making it contradictory. This hyper individualism is easily illustrated by the selfish appropriation and hoarding of land and resources we see today. Everyone should be free to be independent so long as that doesn't require taking independence from someone else in the process. The social nature of human beings is an intrinsic trait that evolved with us. Our hunter gatherer ancestors wouldn't have survived without collectivism.