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.
"Other conditions being equal, if one force is hurled against another ten times its size, the result will be the flight of the former." -- Sun Tzu, The Art of War
'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.
A pause from Is Manipulating Someone An Evil Practice? to share philosophy from past years:
Today is: 17th June (GMT), in history on the 17th of June, 1957 AD the following birth happened:
Philip Chevron: English pop musician (Pogues-Peace & Love)