Good thing I didn't compare fusion to perpetual motion, then. I was pointing out that his too-simple approach could be easily misapplied, and picked an especially obvious negative example to counter his especially obvious positive one.

At this point we just don't know whether fusion is like airplanes or whether it's like perpetual motion. Unless you are proposing building an actual star, the existence of stars tells us approximately nothing about whether a fusion-based power plant is economically achievable in our lifetimes.

I think it's an interesting idea and I'd love to see it happen. But I think it's important to be realistic in our discussion of it.