The survival of all living things depends on maintaining a highly organized (low entropy) state. Bombs, bullets, knives, sticks and stones all kill by increasing entropy in one form or another. Throughout our existence as a species, we have continued to developed different ways to kill each other by increasing entropy. Until recently, the direction was in creating bigger and bigger bombs. Fortunately, we tend not to use our biggest bombs because of the associated collateral damage. Devastating a city with a nuclear weapon renders it uninhabitable and creates a big mess that needs to be cleaned up. The simplicity of the method and the problem of collateral damage create a natural limitation on the development of entropy based weapons. From an evolutionary point of view, the welcomed transition has lately been from bigger bangs to smarter bangs.
The use of poisons to carry out mass killings represents an extremely dangerous evolutionary step in the wrong direction. Unlike the simple act of increasing entropy, killing by non-entropic means is complex and limited primarily by a lack of scientific understanding. Our current knowledge in the areas of pharmacology and microbiology only scratches the surface of what there is to know. Research into these areas is driven full steam by the goal of promoting health. Unfortunately, every new discovery also enables the development of non-entropic weapons. Unlike with entropy-based weapons, where the task in simple and there are natural checks to unbridled progress, the development of non-entropic weapons has no natural checks and will always have the benefit of continued scientific advancement. Non-entropic weapons represent a greater threat to us as a species, not because of what they do, but because of what they can become.
Humans have a way of adapting to change. Equating non-entropic weapons with entropy-based weapons is the first step in a slippery slope towards their wide-spread acceptance. I am not sure if death by non-stop convulsions or by drowning in ones own secretions is any worse than having ones flesh destroyed by the entropic forces of bullets or bombs. What I am sure of is that the wide open future of chemical and biological weapons makes them a far greater threat to the long-term survival of our species.