Is effective communication a way to manipulate others?
Sometimes may be the perception that using effective communication techniques is a way to manipulate others.
This depends on the purpose you use effective communication techniques.
If the purpose is to persuade others, trying to convince them while respecting them, with the intention of mutual growth, then it is not a manipulation.
If the purpose is to act solely for our own advantage, without respecting others and without ethics, then it is a form of manipulation and should be avoided.