This deserves more than a one-legged response, and I hate to choose between friends, but I think Ross Douthat rather gets the better of Damon Linker here.
Linker’s whole project – “the liberal bargain” – rests on the proposition that absent a neutral arbiter without metaphysical commitments you inevitably get social conflict. I pretty much disagree with that proposition whole-hog – I don’t think liberalism is (or can be) a wholly neutral arbiter without metaphysical commitments (indeed, I think this partly because I agree with some of liberalism’s metaphysical commitments); I don’t think such an arbiter would enable you to avoid social conflict (what would compel the loser to abide by the verdict?); and, for that matter, I think you can have devastating social conflict without any real disagreement about metaphysical commitments (those metaphysical commitments themselves may in many cases be “superstructure” rather than “substructure”).
Myself, I would like to see a liberalism that is both more confident and more humble about its own truths. More confident: don’t defend the sexual revolution by saying, “why not?” but by saying, “here is what we have gained – here is the positive good, here are the virtues of the life we now lead.” Don’t attack creationism by saying, “that’s smuggling sectarian religion into the public square” but by saying, “science is a magnificent human achievement that you are defacing, and science matters too much to me to stand idly by while you do that.”
And, by the same token, more humble: recognize that communities with illiberal commitments are bound to continue to exist (and spring up) within liberal societies, and that liberals need these communities as a check on themselves, and cherish them, because they (liberals) are only human, as fallible as any other humans, and as prone to dogmatic certitude. Cultivation of skepticism and doubt will never be enough; you’ll need actual alternative certitudes to push against to be sure that you actually know anything. And, if you’re really a liberal, you have to leave open the possibility of being convinced that one of your liberal truths is actually, well, false.