You are wrong. This kind of example addresses the argument at its core.
Being "antifragile" is all about how you respond to low probability tail events such as this one.
If you become weaker as a result of such an event, you are not antifragile. You are fragile.
If you can withstand said event, you are not antifragile, you are just robust.
If you become stronger as a result of such an event, only then can you claim to be antifragile.