Mainly I don't want them because I don't want a machine instantly making life or death judgements. It might be fine if it mostly informs a human who ultimately pulls the trigger, but having that failsafe is important in keeping machines from going on killing sprees.

I also want people to be held accountable when they do unjustified killings. AI weapons make it FAR too easy to simply pass off a killing as a "woopsie doodle." It's just not acceptable to say "The algorithm made a mistake, version 23 will do better".

I don't have a problem with the AI providing additional information to it's user, but when that's incorporated into a weapon it's a short distance from that to completely automating the killing.

That's why I'm completely against AI weapons.