A few things: In tourist areas they will feel comfortable talking about the protests/reprisal because they get inundated by American tourists wanting to ask them about it. "It’s a tourist destination you have to buy tickets for" -> Right, Tiananmen square has no stigma at all, but that is different from the 1989 incident.

If you post about the 1989 incident on Weibo, it will absolutely get removed and you might get the local police visiting you -- depending on how much time they have on their hands and how incendiary your post was.