I would not ask an Eminem to change their name as soon as they joined. As far as I know, the rapper is not associated with the terrorist group, and it would be a stretch to say the name is offensive because of what the person has sung about. If that were the case, most rapper names would not be allowed in our servers. If we scrutinized all names like that, many of them would not be allowed. Almost everything can be twisted into something inappropriate.
Now if Eminem joined and started making racist comments, it would be handled accordingly. But New001 could make the same comments and receive the same attention from the admins. I don't believe Eminem is known for "hate lyrics", more for just being generally offensive. For that reason, an admin might decide to keep an eye on any Eminem in the server, see if they're going to stick to some Eminem theme, but the name itself isn't really making any statements.
Direct references to very offensive things would not be allowed obviously. An inoffensive name that could reasonably be linked to something offensive will be discussed and is mostly up to the admin (admin discretion). I understand what you're saying about the name and why someone might choose it, but its link to something offensive is too obscure to put a blanket ban on the name.