There is a difference between a discussion/debate and, as dogstar pointed out, proselytizing. Debates are fine for subjects based on facts where evidence and examples can be supplied to support statements, but with a topic of "beliefs" - there is no doubt to be varying, subjective comments and opinions of people's truths. How can you doubt another person's belief? You may disagree with it, you may ask how it was developed or what is the foundation for it, but in no freakin way can you deny it is the individual's belief! And, I certainly wouldn't expect a practicing Christian to invalidate or judge another's belief (LOL).
A belief - A creed. Hail to the heavenly group that unites us in heart and mind. Rock on Heavenly Creed!
The earth is a voice speaking to you.
Take all this pride and leave it behind
Because one day we die.
Believe what you will That is your right....