I think what he is suggesting is that a large adult male is capable of inflicting grave bodily harm when using a baseball bat as a weapon. I'm confident that in nearly every jurisdiction lethal force is justified in such a situation both legally and morally. I do not see him saying shoot the perp. I also do not see him saying shoot to kill. In fact I'll hazard a guess that the OP also knows that he if forced to shoot is only shooting to stop the assault.

Although I understand the behavior of the cyclists I also think it will hurt them in the end, or at least not help them.