Not all countries. Iraq has a bioweapons program: https://en.wikipedia.org/wiki/Iraqi_biological_weapons_progr... at least in 80's, and probably into 90's, and there's no indication they ever decided it to be "counterproductive", even though they abandoned it out of fear for repercussions for BWC violation. USSR had bioweapons program which it never declared "counterproductive", and even though Russian as USSR successor did, it is not really confirmed the program was effectively dismantled. There are pretty credible suspicions that Iran has an advanced stage bioweapons program, and same is suspected for North Korea. In fact, check out this list by PBS: http://www.pbs.org/wgbh/nova/bioterror/glob_nf.html - may be a bit out of date, but enough to realize "all countries have pretty much decided" is unfortunately an exaggeration.

We already have something very close to automated killing machines: anti-aircraft missiles. Couples with radar systems they can identify hostile and go and destroy them pretty much without human guidance

My understanding was that pathogens are frowned upon because of their mutability. There is a high risk that you end up killing people you weren't targeting...namely your own citizens after your bioweapon mutates into something you don't possess a cure for.

This is not the same problem posed by AI sorting of imagery (Maven) or armed UAVs in general.