Because it is an easy concrete way to stir up reactionary sentiment. The real issues are debatable but complex. But the common folk can all visualize a gallon of water.
Not only that they are trying the same playbook as what was done to nuclear. A new technology comes and activists try to instill fear so as to murder the tech in its baby crib.
The world would be better without nuclear technology! Yes, it can be used to generate electricity in a much cleaner way than other technologies, but its potential to kill so many people has shaped geopolitics for generations. If we could get the energy without the destruction, that would be ideal, of course. But there's an unacceptable chance that nuclear weapons will kill everyone I care about.
I think AI is actually similar. It's really useful for all sorts of stuff - I'm running multiple agents writing code as we speak. But it's also going to make the world much more dangerous by giving people the ability to kill and spy like never before.