What has he done to deserve this?

It has nothing to do with disliking learning. Trying to learn and use a system of measurement without being immersed in it is really hard. For years, I've set all my temperature measurements on my phone and thermometers to Celsius, but because I'm surrounded by people and systems that don't use metric, I have to convert back and forth between the two. It's a lot of mental effort for basically no gain.

Every day, customary speed and distance units and my intuitive understanding of them are reinforced when driving and seeing street signs. I know how long a kilometer is, but if you say "My brother lives 45 kilometers away", I'd have a difficult time truly understanding that. I wouldn't be able to estimate how long it would take to drive there, for example.

Another issue is cost. In my job, it would take weeks or months to update all of the documentation and code to metric. Then customers would have to approve of all those changes. A whole bunch of machinery still uses customary units too, so they would have to be replaced or updated.

I say all of this as a metric lover and evangelist. It's not trivial to convert an entire massive country to metric. Countries that have converted already should be hugely proud of themselves for accomplishing a difficult task.