I've not seen the film Tombstone, so maybe that's why I never saw Doc Holliday (as a name, not the player here) as a problem. My immersion in the Sirius Sector was never broken.
It was broken when I came across a furry Liberty captain one time. That's why we have rules like this to enforce.
Other imports such as the The.Joker and his Thugs was technically rule breaking but that guy gave a lot of players some of their best experiences on this server.
This was all at a time of having Star Wars, Homeworld and other such imports though so maybe the vibe was different I'll admit.
I'd say let Doc keep the name. Has anyone actually complained about it?