in the west, we have long argued that the way to build stability is via democracy, by converting the conflicts into debates, where we fight with our words and war with our essays. that is the point.
universal truth is evasive, granted, but mearsheimer consistently misses the point. in russia and also in china, they argue that democracy leads to instability and internal fighting, while in the west we desire democracy because it eliminates civil war and replaces it with stability. we may debate in democracy, but we stop killing each other. this difference in perspective is a function of the different historical realities in britain and russia, and they both make sense when derived from their resulting first principles, but there remains a universal truth underlying them: everybody wants stability, we just disagree on how to get there.
likewise, (almost) everybody in the west wants liberalism, but there is a debate on how to achieve it.
i'm neither a liberal nor a realist, i'm an anarcho-socialist. my perspective is to seek a dialectic between realism and liberalism rather than to set them against each other, and to me this is easy: liberalism is a set of ideals and realism is the framework to anchor them in. liberalism without realism is magical thinking, whereas realism without liberalism is masturbation. liberals that don't begin with realism continually fail because they don't live in reality, which is the basis for much of the liberal criticism of realism; those pesky realists insist on their facts, which get in the way of the magical thinking.
it follows that there is really not a conflict between realists and liberals but a conflict between empiricists and magical thinkers. liberalism, in this context, may even be framed as a religion, which erects the familiar distinction between empiricism and faith.