Since no two people think exactly alike, it is inevitable
that you will have disagreements with others. But it is
crucial to speak with respect to someone even though you
differ. Excessive emotionalism is often a sign that a person
is making an attempt to conceal the weakness of his own
argument. The validity of an opinion is not increased just
because the decibel level is raised.

State your side of the argument calmly in a straightforward
manner. When you speak in a condescending manner or with
contempt and scorn, you will usually just strengthen the
other person's resistance. There is a greater chance of
influencing someone to agree with you when you show him
respect than when you fail to do so.

Excerpted from The Power of Words by Rabbi Zelig Pliskin