Manipulation is done all the time. The media, your boss, school system and the government all have their hand in pointing you in the direction they want you to go rather than where you want to go.
'Evil' depends on what's your interpretation of evil. If a double agent is sent into a terrorist organization and does a little manipulation I can hardly see that as being evil.
It is evil and should never be done unless you are out to save the world but most times people do this for selfish reasons.