No, it shouldn't. To believe that aggression is wrong means precisely that you don't want other people to engage in aggression; you want to "tell them what to do" (namely, to not aggress). Alternatively, to "live and let live," as he proposes, would be to endorse aggression. Adopting national self-determination means abandoning libertarianism. Either aggression is wrong, regardless of whether it is politically popular, or not.
I never thought I would see the day when a libertarian argues against an individual's right to self-determination.