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.

It only sounds legit to people who don't understand biology and haven't done advanced laboratory work. Sort of like Michael Crichton novels: superficially plausible but not grounded in any real science.

terrorists can also use annas archive, scihub and equipment they order on Alibaba to build bioweapons and I don't see him losing his mind over those

if you're trying to build a bioweapon shockingly enough the bottleneck is... the laboratory work. What on earth is 'legit' about stringing words together that sound scary, you can't just iterate 'ai bioweapon cyber' in a sentence over and over as if that adds up to actual evidence for an increased risk of any threat. well tbf you can technically because apparently it freaks a lot of podcast listeners out