I don’t know that he claims they’re being ‘deliberately outbred’, that’s just an anti-Islamic version of great replacement theory which would be far-right. His argument is that whatever the drivers are - mostly ill-judged policy from Europe itself - it’s a symptom of the scenario given. In terms of cultural Marxism, yes the far-right have co-opted the term and created a more conspiratorial version of it, but that doesn’t mean it’s not a thing. I studied Sociology at university and one of the modules was about the relationship and crossover between critical theory and MarxIsm. One of my textbooks was called ‘Cultural Marxism in Post-War Britain’, it was freely available in the university library! But now - according to the Guardian and people on social media who have no idea what they’re talking about - cultural Marxism is a ‘right wing conspiracy theory’. They should’ve explained that to my obviously left-wing tutors!