Question: how many Anti-Tank-Guided-Missile systems are used in street crime, robberies, domestic violence, or accidents involving civilians, per year?
Don't get why you're being downvoted - as a half-Croat I completely understand your point (for the non-Balkan people: former Yugoslavia is your to-go source if you need any kind of weapon if you can't get one legally, there is an enormous amount of stuff from the 90s wars floating around).
In the end we are at a trade-off situation: Either we don't send weapons to Ukraine and let Putin take over, raze the country and genocide off the population (they are already setting up "filtration camps" and forcibly relocating Ukrainians to Siberia [1]), and risk that the Baltic states or Poland becomes the next target for Putin. Or we send weapons to Ukraine, blow the invasion forces to pieces, and risk that the weapons will be sold off later on to the highest bidders.
Personally I prefer the latter: no one should be forced to live under Putin's dictatorship and the post-WW2 world order was explicitly created to condemn Nazi-style landgrab operations. If the price of that will be that some ammo gets diverted off to some other warlord, that's bad but acceptable because the alternative is so much worse.
Good point, I just thought on the impact of the weapons in overall low-level criminality or regional conflicts, but I guess if enough Stingers [1] spill around it could have serious consequences on the safety of air travel all around.
The IFF system of the Stinger weapon system is surprisingly robust, and non-trivial to circumvent. It essentially prevents you from locking on to any vehicle equipped with an IFF transmitter (meaning if you point a western-made Stinger at a western commercial aircraft, it won't let you fire at it). As such, I doubt there will be any significant impact from "unsecured" Stinger systems floating around, though that does not negate similar consequences from non-IFF-equipped weapon systems.
Look at the former Yugoslavian countries. The German right-wing terror group "NSU" is suspected to have used weapons from that area [1], the Charlie Hebdo and Paris terrorists did the same [2].
It is entirely reasonable that, similar to the aftermath of the 90s wars, weapons from Ukraine will turn up in every major conflict zone - especially because the current supply from the Balkan is all 30 years old decrepit shit, whereas Ukraine (rightfully) got the very best of the best of Western weaponry.
The stuff the NSU was using can be bought either at Munich main train station (if you know who and how to ask) or just across the Polish border. They used a single Makarov, mostly. And those were basically available for a 5 DM back when the Soviets retreated from the former DDR.