Except they kill humans all the time.
I think it’s just easier to accept that there is an unexplained reason why humans can generate some kind of power that’s useful to the machines for something at some point between the winning of the war at the point of the movies.
Just ignore the fourth movie.
You should check out the BBC guidelines for subtitling. They are really good and include preserving the intent of the program, avoiding ambiguity, and not spoiling jokes with bad timing.