My guess is that you misunderstood the original word they used "歹徒", which is more like "gangster, villan".

And the clip you referred to, I think was the "tank man" video being aired by CCTV on 1989/6/5, with voice-over as:

"稍有常识的人都会看出，如果我们的铁骑继续前进，这个螳臂当车的歹徒，难道能够阻挡得了吗？摄像机拍下的这个画面，同西方某些国家的宣传恰恰相反，正好说明了我们的军队，保持了最大限度的克制。"

which roughly translates to:

"Any sane person can see that, if our 'iron horse' keeps marching, this 'gangster' wouldn't stand any chance, just like 'a mantis trying to stop a chariot'. In contrary to some western media had claimed, this clip showed that our troops remained utmost desciplinary."

So I would say the clip was used to reinforce CCP's official tone on the tragedy, which is something like "some gangsters colluded with foreign influences tried to overthrow Chinese government".

I know sometimes CCP's propaganda sounds dumb, but definitely not that dumb as "tank man was trying to rob the tank".