Same happened to us and it got ugly. Some of them got hurt though.
Often wondered what happened to those fellows from MN.
We never had any problems but the picketers had a very limited public space to use and two armed guards at the gate. We also parked around the backside of the building in a big courtyard type of space.
They didn’t have anything to offer that was worth the restrictions that would be placed on us by the company if we accepted a troublemaking big union. We didn’t make as much but we had good PHP insurance, a good working relationship with the company and most important, each employee was an individual and could work out extra sick time or other time off with the company. We did have scale pay which I hated.