When you are challenged about what God thinks, says or does, the Bible is the only sensible reference point.  The best way to deal with opinions about God, is with God's Word.  That was what Jesus did when He was challenged by Satan's wrong opinions of Him and Father God (Matthew 4:4, 6, 7).  Jesus uses the same approach with the religious leaders and legal experts when they accused Him of not keeping religious rules.  He pointed them back to the Bible which they claimed to understand.

Jesus referred them back to King David, who they revered.  1 Samuel 21:1-6 tells the story of hungry fighting men who were given consecrated bread that was reserved for the priests; David believed it was right, and so he personally gave the consecrated bread to his famished troops.  Jesus agreed that it was the right thing to do.  God's purpose in giving the law was to protect people, not to starve them.  But as is often the way, religious people cannot see the wood for the trees ... and the more obsessive the religion, the blinder they get.  Blind about how wisely God provides for His people and how He jealously guards them (Joel 2:18).

When your friends offer a religious opinion - take them seriously but be honest in saying that your opinion must come from the Bible ... and discuss what the Scripture says.  You will be surprised how much colleagues will respect what you say, when they know where it comes from (Acts 17:11).  Try talking with your Bible open - even showing them the verses that will address the matter face on.  You may not win an argument, but it will speak volumes about how you trust what God has said.

Many people have never even thought that there might be any value in reading the Bible.  Or they may remember some stories and assume they understand its meaning.  But you can start by reading it with them.  They may need help to study it (Word@Work may be a useful resource for people who want to find out about Jesus).  Don’t argue, but read it with them and answer their questions as best you can.  2 Timothy 2:24-26 says, "And the Lord's servant must not be quarrelsome but must be kind to everyone, able to teach, not resentful. Opponents must be gently instructed, in the hope that God will grant them repentance leading them to a knowledge of the truth, and that they will come to their senses and escape from the trap of the devil, who has taken them captive to do his will."   It might be the first time that your friend or colleague has thought of reading the Bible. But when they pluck up courage to read it for themselves, God will speak to them too.