There's no such thing as fair allocation of a scarce resource. Offering it at a surcharge is, in my not-disingenuous opinion, the least unfair option for this particular one.

Outright reserving it for tall people is discrimination against the short. There are other reasons someone might want the emergency row which are just as legitimate, knee surgery leaps to mind. Should we make a comprehensive list? How do we determine if someone is just lying to get the premium leg room?

I'm open to the argument that the federal government should mandate a larger minimum seat distance. But then, I'm not poor.

As I said, there's no fair way to allocate a scare resource, only degrees of unfairness.