In fairness, this has changed a little in recent years as at least some academic liberal philosophers have been willing more seriously to engage the arguments of libertarians and of social conservatives like John Finnis and Robert P. George. It was also, I think, more an American phenomenon than a British one, though that may be because the center of political gravity is in Britain further to the left than it is in the U.S. In any event, during the period in question one could often find the most serious responses to thinkers like Hayek and Nozick coming from socialists rather than liberals. The work of G. A. Cohen is exemplary in this regard. Cohen is perhaps the most formidable socialist thinker writing today. His book Self-Ownership, Freedom, and Equality is among the best things ever written on Nozick, probing Nozick’s position in depth – and defending it from more superficial critiques – while trying to find some way of avoiding his inegalitarian conclusions. If your views are anything like mine, you will find Cohen’s conclusions completely unacceptable. But you will also find that his arguments and analysis are fascinating indeed and repay careful study.
The esteemed David Gordon reviews Cohen’s latest book Rescuing Justice and Equality, at length, here. Like much of Cohen’s recent work, the book is a probing critique of mainstream egalitarian liberalism from a position further to the left. Cohen is the guilty conscience of academic egalitarianism, always challenging his colleagues to be more consistently egalitarian. He is certainly more interesting than Rawls ever was. Rawls is at bottom a mere liberal apologist, and not a good one either, considering that he never seriously considers the most formidable challenges to his basic liberal assumptions. Cohen is a serious critical analyst of his own deepest commitments. His egalitarianism is unflinching, but he at least tries to meet the other side at its strongest point.