As far as I know, they were declared persona non grata and asked to leave Ushuaia.
But a mob (not related to war veterans) intercepted the convoy and started to throw stones. And yes, here in the Third World throwing stones, stopping the traffic in highways and, sometimes, to burn buildings are regular methods to deal with problems. Not proud of it, but it is just a fact.
In my very humble point of view, the Top Gear crew went here asking for trouble (at least, they paid some websites to "note" the car plate...) and SOME people responded with the current uncivilized mood (fueled, again in my very humble opinion by the government)
A two way shame.