We are all Stoppers now

Harry seems to finally coming closer to defining just what a 'Stopper' is, beyond being a catch-all term for anyone he dislikes who is 'anti-liberation'. It now includes anyone who went on a demonstration against the war, it seems. Unless, of course, he has some secret sources (or maybe magic psychic voices in his head) that tell him exactly what someone believes about everything based on these two sentences:

I recall going to London for a demonstration with about a million others. There was no trouble whatsoever.

Even Googling the name of the writer doesn't seem to bring up his name on the Official List Of All Stoppers Everywhere that I presume Harry maintains to keep up with actions of this nefarious bunch.