Thing is: Believing something doesn't necessarily make it so, Cap. And, odd-sounding or not, according to the many dictionaries I've looked into since wwh brought this topic up, peremptory can be correctly applied directly as a description of a person. There are many examples included in various dictionaries, and I've noted several of those above. This is not to say that peremptory may sit better in many people's minds as a description of manner. Peremptory manners are all fine and well--and sometimes annoying. But it is completely acceptable to describe a person as being peremptory, whether that usage sounds odd and unacceptable to your, wwh's, or anybody else's ear.