[k0k0r0]

Using a different then my own true reasoning is completely normal, and everybody does this. One adjust your reasing to the understanding of the other person for example. Moreover, there is like a miles wide gab between rhetoric and manipulation.

[elif]

utilizing deceit to change someone's behavior for your own personal reasons is, by definition, manipulation.

communicating your true feelings and intentions is the only way to grow trust. what you are describing is needlessly eroding trust.

[shkkmo]

It is perfectly fine to present alternative reasonings to convince someone of something as long as you don't pretend that reasoning is the basis of your own position.