Do you mean, like, Bentham, Mill, Locke, Hume, and later Rawls, etc? They’re all worth reading. They’re not liberal in the popular sense of the term, but they clearly reveal what Marxists say about liberalism being the ideology of capitalism and about the relationship between fascism and liberalism. If only liberals (a) read them, (b) paid attention, © accepted that what liberal theorists say they mean by liberalism is exactly what they actually mean, and (d) didn’t apologise for all the racist, sexist, and classist shit that clearly underpins liberalism.