‘Tell the truth about China!” has become a rallying cry for protesters in Hong Kong. It is exactly what demonstrators in Beijing’s Tiananmen Square were saying 30 years ago, before many of today’s protesters were born. The truth is that for all China’s economic advances, it remains a brutal, dehumanizing tyranny in which the ruling Communist Party would rather destroy people than give them a genuine say in their government.

I was in Beijing in 1989. I witnessed the Tiananmen uprising and during the long night of June 3-4 saw...