If you truly believe in something, is it always right to defend your convictions in all situations?  What if in engaging in such defense of your beliefs, you end up harming your relationship with the person you are debating with?  On one hand, you want to just "lay down the law" and defend your faith, but on the other hand, doing so might make you appear arrogant, condescending, and stubborn.  So what is one to do?

Engaging in such defense of one's faith is what Catholics refer to as "apologetics".  When done properly, it can actually end up having an evangelizing effect; however, when done poorly, it can have a detrimental effect.  In some cases, there are situations in which upsetting another person may harm an important interpersonal relationship with a friend, or someone that you want to become your friend.  In such cases, the arrogance that you may project in a "know-it-all" attitude is pride, a capital sin, in the eyes of God.

Here's a good rule of thumb to follow.  The way I see it, I'll engage in apologetics only if I am questioned on an aspect of my faith.  Otherwise, if all someone else is doing is ranting about why he or she hates Catholics, without asking me any specific questions, then trying to stuff your beliefs in their face because you can't handle a little criticism is evidence of poor self restraint, and an inadequate sense of humility, an all-important catholic virtue.