I suppose this really has a bearing on the last post, but when I was a young Trotskyist, a phase that lsted for exactly the length of time I was madly, deeply in love with Sue BM, she was a Trotskyist, I was seventeen. What we used to do, there were less than twenty of us, but we would join a protest, such as 250 midwives respectfull requesting slightly higer wages, with as many plackards as possible to hand out, each with our logo on it, but bearing slogans like "More Pay", everyone wanted one. It gave the impression everyone was millitantly left wing, especially if there were red flags to wave, the absolutely best thing was to get to a microphone, especially if one's fellow Trots, understood their job was to cheer loud and hard.
I developed a cunning plan to take over the local Literary Society, which in Guildford had rather nice premises, by getting my friends to join and vote out the existing members.
I can't help thinking these techniques are widely used nowadays in politics, it is much easier with focus groups. I remember discussing this with someone who had done a study on the decline of female religous orders, she saw the same techniques coming into play in the 70s/80s, it was so easy with women who were accustomed to obedience to follow a more radical extremist. I am sure we see it in the catechetical movement of the same period.
In secular groups such as those who form public opinion it is easy for a particular group to take over and give new direction first of all with that group and then to use the the group itself to alter the opinion and outlook of society: the BBC for example?