Dobson's book is excellent. I liked Verbal Judo by George Thompson (1984 & 1993). The Gentle Art of Verbal Self Defense by Suzette Haden Elgin (1980, 1983, 1987, & 1989) are also good resources. There are a few sites on deescalation. Remember that enviromental awareness, posturing & positioning (not in a fear response), and good manners is always the first line of self-defense.
Since this is an Aikido forum, always first blend and try to see the other side. Listen first.