The British tried to hold democratic elections during that time, but it was the Communist Party that pressured them not to. The riots you're talking about were Hong Kong Communist going against the British.
I read wikipedia. I just realized that the suppresion is more brutal than what I imagined. Are u referring to HK 1997 election? That election is after the British reluctantly agree to handover HK. From the CCP point of view the elections is a plot to sabotage the Handover. It is not that iI agree or disagree with CCP view or British motive. There are many anti colonial politicians in Asia suspicious of the British motive.