They avoid the realm of patent warfare until they purchase relevant patents.

Yes, when it became clear Apple was going to continue to rely on patent warfare as a business strategy, they secured patents.

So you are saying that sometimes swinging the patent stick can be right?

If someone's swinging it at you, then it's understandable as a method of self defense.

But there are many ways of inflict damages, patent lawsuit is just one of them. Why is this weapon special? If it is inherently evil, then using it under any condition should be condemned. If it is not, then again why treat it like it's special?

>If it is inherently evil, then using it under any condition should be condemned.

Perhaps the legal system is misguided to consider violence in self defense different from unprovoked violence?

No, but I do not consider violence inherently evil either.

As a matter of fact it seems most people do not consider violence inherently evil, it is unjustifiably glorified in western culture I'd say, by western I mean American, by American I mean US.