The reason the life sciences are resistant to regulation is at least partially because they know that killer plagues are several orders of magnitude harder to make than Hollywood would like you to think. The biosphere already contains billions of species of microorganisms evolving at a breakneck pace, and they haven't killed us all yet.
An artificial plague has no special advantages over natural ones until humans get better at biological design than evolution, which isn't likely to happen for a couple of decades. Even then, plagues with 100% mortality are just about impossible - turning biotech from a megadeath risk to an xrisk requires a level of sophistication that looks more like Drexlerian nanotech than normal biology.
An artificial plague has no special advantages over natural ones
Artificial plagues can be optimized to for maximum human deaths, something natural plagues aren't. Artificial plagues can contain genes spliced in from unrelated species, including the target. For example, human hormones.
The FHI's mini advent calendar: counting down through the big five existential risks. The second one is a new, exciting risk: synthetic biology.
Synthetic biology
Current understanding: medium-low
Most worrying aspect: hackers experimenting with our basic biology
Synthetic biology covers many inter-related fields, all concerned with the construction and control of new biological systems. This area has already attracted the attention of bio-hackers, experimenting with DNA and other biological systems to perform novel tasks – and gaining kudos for exotic accomplishments. The biosphere is filled with many organisms accomplishing specific tasks; combining these and controlling them could allow the construction of extremely deadly bioweapons, targeted very narrowly (at all those possessing a certain gene, for instance). Virulent virus with long incubation periods could be constructed, or common human bacteria could be hacked to perform a variety of roles in the body. And humans are not the only potential targets: whole swaths of the ecosystem could be taken down, either to gain commercial or economic advantages, for terrorist purposes, or simply by accident.
Moreover, the medical miracles promised by synthetic biology are not easily separated from the danger: the targeted control needed to, for instance, kill cancer cells, could also be used to target brain cells or the immune system. This would not be so frightening if the field implemented safety measures commensurate with the risks; but synthetic biology has been extremely lax in its precautions and culturally resistant to regulations.