The usual reminder that laser fusion research is done not for potential energy production, but for development of thermonuclear weapons: https://news.ycombinator.com/item?id=25210756
"The mission of the National Ignition Facility ib to achieve ignition and gain in ICF targets in the laboratory. The facility will be used for defense applications such as weapons physics and weapons effect testing, and for civilian application, such as fusion energy development and fundamental studies of matter at high temperatures and densities. This paper reviews the design, schedule and costs associated with the construction project."
So, "fusion energy development". It's sorta both.
https://inis.iaea.org/collection/NCLCollectionStore/_Public/...
And most research fields are not practical at some point in their lifespans, that doesn't mean it will never be practical, or we won't (hopefully) learn things which make other energy technologies practical.
Sure the results can have other uses, but that's not why LLNL gets millions each year for running the NIF.
Yes, they have stated that the nuclear research labs were contacted by the military; but this occurred after the reported test. Its a stretch to claim that the project is thus military.
There are some interesting issues though: prior generations of nuclear weapons production involved massive release of highly toxic byproducts. In addition to better control and containment, one would reason that processes with less toxic byproducts would also be desirable.
So how do you purify the plutonium cleanly? How do you cut and weld the plutonium to manufacture the parts, cleanly? And how much of this can you tolerate and still produce weapons-grade materials, and weapons-grade parts?
Given some modifications in design to accommodate the environmental restrictions, you need to model the reactions to make sure the new designs work. But even if you model everything, you need to validate the models. So you have to test something. So you need to produce high energy plasma for primary and secondary designers to validate their models and their designs.
The NIF is a weapons lab instrument for studying fusion reactions. The current hollraum is plutonium, designed to irradiate a deuterium-tritium target. If that doesn't sound like a primary acting on a secondary, I don't know what does.
All that is just a high-level counterargument. The real argument though is quite straight forward: LLNL (home of NIF) is a weapons lab. They are not in the nuclear power business.
This is a super explicit part of all the NIF press releases, and these "stewardship" experiments is what they were doing most of the time last year and. Here's a quote from the LLNL press release as an illustrative example:
“This result is a historic step forward for inertial confinement fusion research, opening a fundamentally new regime for exploration and the advancement of our critical national security missions. It is also a testament to the innovation, ingenuity, commitment and grit of this team and the many researchers in this field over the decades who have steadfastly pursued this goal,” said LLNL Director Kim Budil.