I may have been mislead on this (not a good situation for the bureaucrat doing 95% of the namechanges on en.wiki) but my understanding is that en.wiki does not permit forced name changes. Barring an order from the Arbitration Committee, Jimbo Wales, or the Foundation Board, I just don't think we can do it. I'd be interested to hear from Angela, who is also an en.wiki bureaucrat and has far more inside experience than I do.
If you ban him the name will never be available for Wikimedia to use. A forced name change is far preferable.