First question:Originally Posted by whl626
"You are actually preaching to somebody who is on your side" means the person is talking to somebody who already agrees with him. The speaker is saying to that individual that he would be better served by talking to people who don't already share his point of view. (Please let me know if that is an adequate explanation.) An American idiomatic expression for that is preaching to the choir. If you are preching to the choir you are talking to people who already agree with you.
It is context which gives any statement its meaning. If someone accuses somebody of taking his statement out of context he is saying that person is using his statement in such a way as to suggest a meaning he (the original speaker) did not intend.