I have no doubt that biological weapons have been developed to some degree, somewhere, in a well-funded government lab, in complete secrecy. But that is not a problem. This secrecy is what saves us from a race to the bottom. Some government will develop a limited capability of biological warfare. They probably already have. With no information about what their adversaries are doing, they will simply stop. As far as they know, they have developed a state-of-the art biological weapon system, and they are probably correct.
One of the reasons that the nuclear arms race happened, was the "openness" of the competition. You can't hide a nuclear explosion. Your adversary knows how sophisticated you are, and they now have to push 1 step further.
Biological warfare doesn't have to be like this. Be sure that some Darpa or DoD funded secret project is working on countermeasures, but there's another interesting thing:
You can stop biological attacks by quarantine. It's very simple, very effective, and doesn't require developing Armageddon-tier weapons in the process. Another issue that's purposefully isn't discussed in the video is how effective the delivery of these weapons are. Simply put, not very. Viruses, the main attack vector, change in every iteration. There's no guarantee you can infect that many people with an intact version of your weapon. Sooner than later, you genocidal weapon will stop being so selective, because it's evolving for it's own benefit, not yours.
And finally, if you really are concerned about this issue, as you should, the right way to fight against it is to find a way to stop the infection and proliferation, to find ways to stop these attacks without accelerating weapons development.
There are ways to fight these weapons without building them, and you can definitely do better than starting a public campaign that asks people to develop horrific bioweapons just so we can find a way to stop them later on, maybe.