If someone demands freedom and democracy, there is really no good argument against him. You just have to concede and go along. But if someone makes a further claim, as some pan-democrats have done, that only full democracy can resolve or at least soften deep divisions in our society, that's highly debatable. The opposite argument - that it will exacerbate conflicts between different classes, vested interests and groups, and may even make Hong Kong-mainland relations more difficult - seems to me to be equally, if not more, plausible.
There is little empirical evidence that democracy calms tensions and conflicts. Pay a visit to Istanbul, Sao Paulo or Brasilia, Cairo, Tel Aviv or Jerusalem, Santiago, Athens, Madrid, Jakarta, Sofia or Washington. These democratic cities and societies are as deeply divided and conflicted as Hong Kong in their own ways. I rather think people in "undemocratic" Hong Kong are divided like everyone else precisely because we are free, and legally protected, to air our grievances like any free and democratic society.
There is also no firm theoretical basis for the calming influence of democracy. While Western democracies have successfully resolved what has been called the "tyranny of the majority" problem, most if not all are plagued by what may be called "the tyranny of the minority" - activists obsessed with and committed to a single issue, say, abortion, farm subsidies or, in Hong Kong, where to put an incinerator. Their demands often override majority preferences.
Well, what about "the widening gap between rich and poor, the decline in opportunities for young people, the worsening housing problems, and the increasing inadequacy of our pension and health care systems", as a prominent pan-democrat said of the failure of governance in Hong Kong. These problems have more to do with market economics than democracy, and many democratic governments have trouble achieving any consensus to tackle these deep-seated, almost universal, problems.
There is also no reason to think a democratic Hong Kong would be friendlier to Beijing or to mainlanders. But Hongkongers are pragmatic, you say. If that's true, why not accept the status quo? The truth is that the pan-dems cannot guarantee democratic Hong Kong will never challenge Beijing on key sovereign policy issues any more than Beijing can guarantee it will never interfere in our domestic affairs. The pan-dems demand Beijing take a leap of faith in Hong Kong democracy while having no faith in Beijing's intentions. Trust can only work both ways.