Point #2 isn't weak, because it scales with the number of users. Slow sites waste not only energy and money (through electricity bills and device wear) × number of users, but also user's time, again, × number of users. If you want to count human time, then that extra second or three your thousands of users have to spend waiting for your site to load easily adds up to justify getting an engineer to muck around your site with a profiler for couple of hours and identify hot spots, and then more hours (over next days) to fix them.
I wish the "human time" ethical cost was factored in elsewhere besides just software. Things like: redundant forms at the doctor's office; useless fences that prevent you walking the shortest distance; time-consuming preambles when you call any customer service number. Imagine if the amount of time wasted was instead converted to a single number, divided by the average lifespan, and the corresponding number of people struck dead.
The argument for users time is a good point, but I don't think the author was intending that. My point was just that it was not sufficiently argued to be obvious.
However, even that does not make the case that web performance is an ethical issue. It would only do so when the number of users is much greater than the amount of effort it takes to make a site.
If I make a site that I expect 1000 people to look at, then the performance of that site isn't really significant. And not an ethical issue.
There's a categorical imperative aspect to this: a site with 1000 daily visitors (not necessarily unique) is not big enough to make its performance a significant issue. But if all such sites think like this, then it suddenly becomes an issue.
