I really don't think it's unreasonable or bad for someone to avoid other cultures. I think it's bad to be ignorant of other cultures, and certainly to be intolerant or bigoted, but I think it's perfectly reasonable to want to live and be around people who largely share your culture.
I don't disagree with that, but cultural isolation is a strong term with strong connotations for me.
I think history shows us that if it's easy for people to remain ignorant of others through cultural isolation, some subset will do so. I'm not against people carving out a cultural niche, but I think that the point we can use the word isolation to describe it, we have a problem. The problem isn't one direction, either. Cultural isolation can keep outsiders from understanding and tolerance as well, which leads to discrimination, which may lead to more isolation and reciprocated feelings towards the outside.
