By the time people start to realize what's going on it will be too late.
Not that the meat industry would ever score an own goal like that.
https://en.wikipedia.org/wiki/Bovine_spongiform_encephalopat...
It doesn't matter much if the AI can give perfect "explain like I'm 5" instructions for making VX. The people who carry out those instructions are still risking their lives before claiming a single victim. They also need to spend a lot of money amount on acquiring laboratory equipment and chemicals that are far enough down the synthesis chain to avoid tipping off governments in advance.
The one big risk I can see, eventually, is if really capable AIs get connected to really capable robots. They would be "clanking replicators" capable of making anything at all, including VX or nuclear weapons. But that seems a long way off from where we are now. The people trumpeting X-Risk now don't think that the AIs need to be embodied to be an existential risk. I disagree with that for reasons that are too lengthy to elaborate here. But it's easy to see how robots that can make anything (including copies of themselves) would be the very sharpest of two-edged swords.
Chemical weapons are absolutely terrifying, especially the modern ones like VX. In recent years they have mostly been used for targeted assassinations by state actors (Kim Jong Nam, Salisbury Novichok poisonings).
If AI makes this stuff easier to carry out then we are completely fucked.