[estearum]

What? That's your second strawman in two comments.

Nobody said you claimed they were harmless. People are taking issue with your assertion that biological agents can be either contagious or lethal (not both), and therefore you discount its risk. This implied tradeoff between contagiousness and lethality simply is not enforced by anything in nature.

The natural emergence of a pathogen that's both highly contagious and highly lethal would be a much rarer event than the natural emergence of one that's either contagious or lethal, but we're talking about engineered pathogens. There is no reason to think that pathogens cannot be deliberately created that are both of those things.