Every act that we do as human beings has a potential negative side to it, it just depends on the intent. May be the salesman was trying to get you a better car, or may be he was just a jerk. May be he didn't know what the customer really wanted. Those situations always exist in everyday life. What we try to do is elevate people up to the level they realize that every word you say has impact.
Every communication has impact.
The more people will know about persuasion, the better. You're in Poland for the second time. I see this country as a young child that is eleven years old now. I think leaving communism and going to capitalism is an extremely difficult change, but for different reasons that people usually think. When prisoners leave prison, they always have the tendency to go back to the prison, to commit another crime.