Agreed. It strikes me that "balanced viewpoints" are actually antithetical to the anti-fragile philosophy Haidt promotes. We need to be malleable in our viewpoints so that we are both free to express them and should be expected to change them when we encounter evidence against them. A "balanced viewpoint" means keeping viewpoints safe from the world (a "fragile" viewpoint!).

It's also worth noting that humans respond better to praise and work more efficiently when we feel safe. So we obviously can't be completely "anti-fragile".