They killed dozens of unarmed soldiers, hanging them by their necks and immolating their corpses. Many of the deaths were done by the mob and they started the lethal violence. They had hundreds of guns out of nowhere, likely supplied by the CIA. Good riddance to these fascist, west-collaborating "students" and the dupes who followed them.

Liberals always handwring at their enemies suppressing internal problems with unsophisticated violence, but that's often the only tool these nations have to sustain their own existence. They don't have sophisticated surveillance deep states with media narrative control, just simple brute force. It's why Liberals were aghast at "Assad using barrel-bombs on his own population" - the preferred method is to destroy street movements via a complex suite of spying, targeted media narratives, sheepdogging, hidden plain-clothes operatives, targeted assassinations of leadership like how Ferguson and the 2020 riots were handled. Assad had one button to have his nation continue to exist, and it was "drop the barrel bombs on the jihadists hiding in apartment complexes" so he pressed it. That makes him a giant villain to Liberals, despite their own funding of jihadists being the very reason he had to push that button.

China at the time of Tiananmen was an unsophisticated state in its suppression capabilities. It had one button to deal with the revolt and continue to exist. I don't believe it was a mistake for them to push it. You can contrast this to how the Hong Kong colonialist petty bourgie revolt was squashed, with 0 deaths. China would obviously prefer 0 deaths, they just didn't have the capabilities at the time.