I accidentally concisely summarized my position on bike helmets in a Facebook comment:

It might be a good idea to wear a helmet, but it’s a waste of passion and effort to try to get other people to do it. Spend the effort and breath you would have spent on helmet debates on making it safer to ride.

This actually sums up my position on a lot of debates. Stop wasting your breath with lectures and debates, and go out and make it easier and better for people to do the right thing (or the thing you think is right). And for the record, this applies just as much to anti-helmet people like Colville-Andersen as it does to pro-helmet people, but there are a lot fewer of them.