These fights are not knock'em down brawls. People are allowed to protect themselves and to fight using equipment. There is very little difference between this and people who fight professionally for money, whether they are MMA fighters, boxers, or they participate in a differnt sport. It is not like getting into a bar fight.
Violence is never appropriate, and especially not when it is simply for the sake of getting a good deal. Material goods are simply objects. There is no way that injuring another person in order to buy an object is acceptable behavior. It is important that people take stock of what is truly important in life.
While I am no pacifist, fighting in general is a bad idea. Conflict may be a part of nature, yet people should try and call on the better angels of their nature whenever possible. Something as visceral and silly as a good shopping deal is never, ever a justification for violence.
The annual fights that occur on Black Friday and Boxing Day are just one more example of why more people should resort to ordering online. There is simply no good reason to fight over a want. Sure, in times of crises, it is not desirable, but it is understandable that people may resort to violence to fight over a commodity. However, fighting over the latest gadget is just not something that society should tolerate.