If you look at the current tactics of insurgency, software is not a part of it. Enemies of the US (Al Qaeda, etc) already had tremendous success with the current insurgency tactics (IEDs, etc) which were low tech solutions, and were vastly hard for the US to overcome.
Why would they go to software when there's plenty of tried and tested low-tech solutions already to kill your enemies?
To kill more people, whilst taking even lower risks themselves.
They probably wouldn't write the software themselves -- they'd get it from e.g. some supportive dictatorship
(With "them", I'm personally not thinking about the talibans, but other groups)
Sarin gas? Nuclear weapons? Truck Bombs? Strapping bombs onto children?
Cheaper and more accessible though. Not many people can build or buy their own nukes or sarin gas.
Obviously correct, so in a sense the parent commenters concerns are not about something new.
But historically these weapons systems are massively expensive custom systems developed by defence contractors for major states. Costs, budget cycles, and technical limitations went some way to limiting their ubiquity and the rate they could gain functions.
So cruse missiles had autonomous terrain-matching terminal guidance, but the US needed the combined abilities of the NRO and General Dynamics / McDonnell Douglas / Raytheon etc to build it.
Whereas now we have free and triviably cloneable software (embedded OSs, drone flight and guidance s/w, ML and image recognition stacks, global mapping data) and a massive range (compared to event ten years ago) of dirt-cheap cots hardware (GPS, lidar, ...)for making autonomous moving objects. And often those devices are fairly thin hardware shells around yet more software.
The network effects driving these capabilities, particularly in software, and their seemingly exponential increase, are what I took to be the source of the parent commenters concerns.