"Ignorant" is often used as a perjorative, the connotation being "wilfully ignorant, and a bad person because of it". I'm hardly surprised that people get upset for being called that. Also, words in general don't really mean anything, though you and Dawkins might discuss things in a context where "ignorant" has no connotation, while it has such connotation among the general public. In that case it would be accurate to say that you are literally speaking a different language.