The rules only oppose using a full name that bears a resemblance to a known individual, to prevent players from essentially just roleplaying someone who does not exist in this universe; using just a last name is not against the rules, regardless of how common or uncommon it is (although it is worth noting that there are at least three significant individuals with this particular last name; Kirit already referenced the baseball player).
Previously this was the same for SW names, which is why so many players have surnames like Skywalker and Fett, but when that rule was changed, it was changed only for SW names, so that now SW surnames are no longer accepted, but other known last names are.
This does mean that someone could join as Bob Disney and it would be approved, but Waltt Disney would not be, if you see the distinction, in case that is a more helpful example to you than 'Lincoln.' Prominence of the last name is not the issue.
I really haven't got anything to say to the original poster's claim of bad taste, considering that is a very subjective area and some are more easily offended than others; that happens. I strongly suspect that no offense was meant by the individual who requested the change; it is not uncommon for players to reference notable military figures considering the nature of this sim. If it's any consolation to you, it is also believed that Rommel was involved in a plot to assassinate Hitler. ;P
“And as for Khan's Avatar...Khan's got enough years to decide what he wants and honestly i love his avatar. ”
I would not support a double standard. If something is deemed inappropriate, it ought to apply across the board. However, I have heard fewer 'indecency' complaints about Khan's avatar than about my own, so I really don't think that is an issue.