On birdsite today someone came dragging the old "[if democracy is so great, why didn't the Brits give it to Hong Kong?]".

Yeah? When every other colony was given democracy or independence in the 60s and 70s, after Britain's catastrophic failure to maintain imperial dominance in India, why didn't they give it to Hong Kong?

Because Beijing threatened to "liberate" it if they did. When Chris Patten introduced partial democracy in 1993, against the will of British negotiators, Deng was furious.