i'm not a linguist, but i think it's ok as long as you mean the lower-case term, nazi. Upper-case Nazi refers to a member of a particular political party. Lower-case, as i understand it, means someone who usurps power at the expense of others in a demeaning and/or abusive way. For example, "The 'President' used his power to immediately cancel or stall a lot of federal programs, even though he knows a lot of people depend on them, the ****ing nazi." That would be okay because it's an expression of your opinion, which you have a right to express, at this time anyway.