You seem to be projecting a lot of things that don’t have a firm basis in external reality. Are the guys with machine guns there to intimidate tourists, or are they there because Tienanmen Square is right in front of the Chinese equivalent of the White House and several other important buildings that require high security? The incident (which, let us be clear, also involved armed insurrectionists with incendiaries and commandeered rifles) wasn’t even the last major violent event in the area, as people did die actually in the Square some time later when Falun Gong members set themselves and a small girl on fire in protest of the group being banned!
The thought police you are imagining seem, if anything, to be a much better case for you being wrong. However you might feel intimidated in the moment, clearly once you left you understandably made a firm association between the Square and machine guns!
Furthermore, you’re making silly excuses for liars. There were people who weren’t even there for the supposed massacre (see the video) who were accounting very peculiar events in lurid detail, like tanks running over inhabited tents and then mulching them and such. Do you think some scared college student is going to have an anxiety-based hallucination that causes them to think they were places they weren’t and saw things that have probably never happened anywhere? When does that happen besides severe schizophrenics and children who aren’t processing that they just had a nightmare?
It seems to me that you are reaching for excuses, especially since you are disregarding the numerous witness, both domestic and foreign visitors, who all saw that there was no massacre in the Square as the media hysterically portrayed. Leaked state documents over the years (from ambassadors and such) only affirm this further. I can look up some if you like.