Are we incapable of fighting anything other than ourselves? Are we incapable of seeing anything other than ourselves?
Without self, there can be no other. When other is diminished, self is diminished, and so too of the inverse. There is a degree of assymetry, organisms do have an "open circuit" as their system of feedback and control, but it would seem that we can't truly engage with anything other than our internal representations of the external world.
Anything we choose to fight is just part of ourselves we ordinarily fight internally, playing out apart from us. Otherwise, we would have little basis to detect and respond to it. Stare into the abyss and all that.