It sounds good on paper, but it actually doesn't make any sense when you think about it.
The whole reason Jack was trained in the first place was to kill aku. Granted aku is pure evil, but he is still willing to kill him with means he doesn't have too much of a problem with killing for the right reasons.
Jack wouldn't imagine the people he is killing as robots because he comes from a time before the very concept of robots existed. If he saw them as demons it would work, but there is no reason for a samurai from feudal japan to even be able to grasp the concept of robots.
There have been multiple times where the fact that he was fighting robots was a key aspect of the story. For example x9 said himself that he was a robot that had emotions.
While it wasn't made clear if he killed those bounty hunters or not, he still clearly saw them as being human. Same with the guardian (although not really human, he still didn't see him as a robot).
It just doesn't work based on what we already know.