Among democrats everywhere, you inevitably find a few demagogues. They are the most extreme, and reject any accommodation and compromise.
They dismiss mainstream democrats as traitors to the cause and run their own fringe groups. But in time, even these more extremist groups are not to their liking; and they go their own way, taking their diehard followers with them. Since their following is often substantial, especially among the young and disenfranchised, they are a substantial political force to reckon with even if they have no real popular support.
For such people, politics is not the art of the possible. Negotiations, the bread and butter of political exchange, are foreign to them. They feed on public anger and resentment, and use immoderate, often coarse, language to denounce not only their opponents, but moderates within their own democratic camp. They are often failures in everything they do, and the only path they have to power and influence is through demagoguery.
In Hong Kong, lawmaker Wong Yuk-man is such a demagogue. The way he and his followers protest must be seen to be believed. Most local protesters don't march in sync, even if they all take part in the same rally. Wong leads his followers into battle with police like a godfather commanding his private army.
Mainstream pan-democrats fear his tactics and denunciations. More than anyone else, he helped blacken the reputation of the Democratic Party for compromising with Beijing over the electoral reform package in 2010. What that party lost in the legislative election last year, radicals like Wong gained. He co-founded the League of Social Democrats with fellow lawmakers "Long Hair" Leung Kwok-hung and Albert Chan Wai-yip. Then he broke off with the league and founded People Power with Chan. Now, he's tired of People Power and wants to boost his own parties like the peculiarly named Proletariat Political Institute. As far as I know, only Leung, not Wong, has ever professed to be a Marxist.
When a community becomes highly polarised, you always find people like Wong. That's why Beijing and Leung Chun-ying should work seriously with mainstream pan-dems on full democracy before it's too late.