This story really defines the difference between radical leftism and just people have a strong political position that they have no problem discussing in detail. The radical leftist cannot separate their political ideology from the rest if their life. It consumes them and it bleeds into every single thing they do. Anyone, anyone at all with a different opinion is considered a threat and must be eliminated. This, in their minds, gives them permission to do anything necessary to remove the threat.
Those with strong opinions can set aside their politics and just take a break from it all. In short, they can go have a bite to eat and not really give a shit who is at the next table. If you can't even stand the sight of a person with an opposing view, so much so that you must find a way to remove them or you have to walk out yourself, you are in fact, more than a little nuts.