[Murray] has argued that the middle-class' efforts to separate themselves from the underclass make the situation worse, not better, because they make it harder to middle class culture to spread to the underclass, and he has advocated attempting to close the chasm in various ways. By contrast in your original comment you seemed distressed that it was so financially difficult for the middle class to separate themselves from the underclass and I got the impression you wished it was easier. Do you disagree with Murray, or was I drawing an incorrect inference from your comment?

Well, even if we assume for the sake of the argument that it exacerbates the problem, this still doesn't mean that it's irrational for individual middle-class people to separate themselves from the underclass. All that this assumption would imply is that there is a tragedy-of-the-commons effect. But this doesn't change the perspective and the incentives faced by individuals at all.

I am reticent about voicing my personal opinion on the accuracy of your description is because I'm afraid I'm skirting the edge of political discussion already.

Don't worry. As long as your comments are polite, well-argued, and made in good faith, you won't break any social norms here. Especially if the discussion is about general and long-standing social issues, and not about the ongoing political controversies from the headlines.