Later I came across someone remarking that such a march is a waste of time, adding that one would be better off taking more practical actions. The comment reeked of William James pragmatism.
Marches are rather like latter-day processions, which have numerous excellent precedents - e.g. the processions with the Ark of the Covenant in 2 Samuel 6 and 1 Kings 8, the triumphant entry of Christ into Jerusalem.
In the case of Friday's event, for this Catholic the march became a form of public prayer attended by Rosaries and hymns involving numerous co-religionists. This is an old Catholic custom, which has been done for centuries during emergencies to implore Divine aid for all kinds of calamities - e.g. war, plague, famine, storms, drought.
Among the participants the public display of a march also serves as a great reminder that - all the efforts of the popular culture and media to suggest the contrary - we are not alone or isolated in attempting to cure a great evil.
I think a favorable word can be added about a public event that has peaceably gathered hundreds of thousands of people each year for over four decades.
In conjunction with other efforts, a march like last Friday's is a crucial and valuable aid.