Anacoenosis

Anacoenosis is a figure of speech in which the speaker poses a question to an audience in a way that demonstrates a common interest.
Discussion.
The term comes from the Greek ("anakoinoûn"), meaning "to communicate, impart".
Anacoenosis typically uses a rhetorical question, where no reply is really sought or required, thus softening what is really a statement or command. 
Asking a question that implies one clear answer is to put others in a difficult position. If they disagree with you, then they risk conflict or derision. In particular if you state the question with certainty, then it makes disagreement seem rude.
Particularly when used in a group, this uses social conformance. If there is an implied agreement by all and one person openly disagrees, then they risk isolating themselves from the group, which is a very scary prospect.
If I am in an audience and the speaker uses anacoenosis and I do not agree yet do not speak up, then I may suffer cognitive dissonance between my thoughts and actions. As a result, I am likely to shift my thinking toward the speaker's views in order to reduce this tension.