no sense to try to reduce any of them!

I think you're misreading Cochrane. He approvingly quotes Pindyck who says "society cannot afford to respond strongly to all those threats" and points out that picking which ones to respond to is hard. Notably, Cochrane says "I'm not convinced our political system is ready to do a very good job of prioritizing outsize expenditures on small ambiguous-probability events."

All that doesn't necessarily imply that you should nothing -- just that selecting the low-probability threats to respond to is not trivial and that our current sociopolitical system is likely to make a mess out of it. Both of these assertions sound true to me.