From misunderstanding exponential growth, which it will jump start. They think people will continue to live as they do now, just with lower electric bills.

Norman Borlaug on receiving the Nobel Prize for the green revolution, said it well:

"The green revolution has won a temporary success in man's war against hunger and deprivation; it has given man a breathing space. If fully implemented, the revolution can provide sufficient food for sustenance during the next three decades. But the frightening power of human reproduction must also be curbed; otherwise the success of the green revolution will be ephemeral only.

Most people still fail to comprehend the magnitude and menace of the "Population Monster"...Since man is potentially a rational being, however, I am confident that within the next two decades he will recognize the self-destructive course he steers along the road of irresponsible population growth..."

We haven't steered away from that course. Fusion would accelerate us on it. If we have to come into balance at some point, why not now instead of when we exhaust fusion's potential? Why does this community think we can solve every technical problem from the moon to Mars to fusion, but we can't live in balance with nature?

Except that we actually have steered away from this course, though not through any conscious decision. More economically developed nations tend to have lower birth rates, with the most affluent somewhat below the rate of replacement. In my opinion, the best method to curb population growth is to get more of the world up to that standard - and energy production is evidently a huge factor. See for instance the work of Hans Rosling.

And either way, energy-intensive practices wouldn't accelerate environmental destruction, they would enable us have a smaller footprint in the natural world through, for instance, vertical farming (currently infeasible because electricity is more expensive than sunlight), carbon capture, switching from aquifers to desalinated seawater, etc.

Fusion and space colonization can get us to sustainably supporting trillions of human lives in the solar system alone. Fundamentally there is no living in balance with nature; the only barrier that can’t be overcome is the heat death of the universe, and there’s no living in balance with that, either.

>> but we can't live in balance with nature?

With greater prosperity comes reduced birth rates. This has been seen across the globe in a variety of cultures. The thinking goes that if fusion, cheap energy, can lift people out of poverty it will contribute to decreasing population growth.

Wealthy countries around the world are seeing collapsing fertility rates and exploding carbon & resource use. We can’t live within balance with nature because of the second item, not the first.

I feel it will be waaaay cheaper than any alternatives though (order of magnitudes, that we are likely forced to be spending on this regardless).

If success was guaranteed money wouldn't really matter.

Though part from success we have deadlines etc. that complicate the matter further. Regardless, this is welcome news.