I think it makes sense but I can also see it from the perspective you have taken and personally, I steer away away from these kinds of registrations.
To my mind the measure of how unethical it is to register other people's names corresponds to how many other people have that name, and the more people there are, proportionally their own individual rights to it decline. In other words if you punched someone in the face, obviously that is a clear wrong, however if you applied 1/10000th of the force of the punch to 10000 people - let's say by lightly brushing past 10000 people walking down the street over the course of a year, nobody would mind.
Preventing one person from having a domain name corresponding to their name is tantamount to a personal attack because you have deliberately stopped a person having a resource that they could find useful, yet is of no use to anyone else. That's clearly unethical.
Whereas if a domain name corresponds to a common name belonging to thousands of people, then no one of them could be said to have an exclusive right to it, and the domain can be thought of as being almost generic. Take john.co.uk for example, that could be perceived as a generic domain (or equivalent to generic) because there are so many people called John. It would also be quite valuable, so if someone called David was willing to pay more than anyone else, no-one would really argue with his right to it, although there might be a few disappointed Johns, but they had no exclusive right to it, so that's tough.
Now if you apply the same logic to a common first and last name combination, say johnsmith, we have a similar situation. It seems
there are about 25000 people called John Smith in the UK. If we treat them all as being equal, you could say each has 1/25000 of the right to the name (and I'm speaking morally not legally, as I'm discussing whether it would be right to register it or not, not what might happen if legal vultures got involved). To my mind, such a tiny claim to the name in practical terms amounts to a negligible right to it for any one person called John Smith. But there would clearly be considerable demand for it and therefore one could invest in it without offending anyone in particular and hopefully make a good profit.