The difference there is that a knife has some obvious, benign use cases. Smart weapons targeting has only one use case, and it's to do harm to others.
When China attacks with AI weapons do you expect the free world to fight back armed with moral superiority? No. We need even more lethal AI weapons.
Mutual assured destruction has worked so far for nukes.
My point though is that this is the only use case for such systems. The common comparisons to things like knives are invalid for this reason.