It's not "legit", it's pointless scaremongering about entirely speculative future dynamics. Current LLMs can't "build" anything novel in this broad space. What if future AIs make it a lot easier for researchers to defend against plausible bioweapons? That's also reasonably possible, and would be a reason to deploy bio-capable AIs more broadly (with meaningful safeguards of course. But these are comparatively cheap because worthwhile bio research is resource-intensive already). At the very least, it'd be nice to have an AI model that doesn't immediately refuse to answer questions about junior-high Biology class.