For usernames ... yes, it's not hard because the list of choices is much reduced, especially if they are case-insensitive. You can actually pre-register all the offensive ones and assert eminent domain over any new ones. For example, "Mohammed", "PapaDocDuvalier", or "Abu_Nidal" are offensive only in certain circles. Unless those circles intersect yours, you should be ok.

It sounds like your site is moderated to some degree. Remember - if your site is successful, one of two situations happens:

1. the less it can be moderated due to volume
2. the more moderators you need to keep up with that volume

I'm not saying anything as to the decision to be moderated or not. Perlmonks is moderated, and has hundreds of moderators, to boot. But, even PM doesn't have automated moderation. A human has to initiate everything.

PM deals with offensive postings to the boards by allowing any post, then having automated reaping if the post is not approved and the reputation drops to -5 (or something like that). The posts are viewable, though, for a small amount of time. And, this is with the lack of accountability of the Anonymous Monk.

User bios are given more latitude here, but the user has to have proven themselves (through the gaining of XP) for some time before gaining all the features. And, still there is community policing.

Unless you absolutely cannot have a single posting be viewable to whomever it might offend (for whatever legal reasons), community policing is usually enough.