I've been noticing a trend in a lot of Christians feeling like they need to defend themselves. So I'm going to share some things that have helped me with this.
An easy way to deal with this is to put more value on what God says about you than you put on what other people say about you. Which do you hold in higher regard? Does what other people think and say about you dominate your outlook? Or do you hold what God says in a higher esteem? It's good to value and respect other people. Even if someone is wrong about something, that person is still valuable. They are valuable to God, and so they should be valuable to you. But that doesn't mean you need to value that person's words or opinion, especially if they are wrong about something. If you only put value on what God says, no accusations or insults from others should affect you. For this to be effective, you need to know what God says. The bible, from Genesis to Revelation, is about Jesus and His finished work. Jesus is God's word. If it doesn't match Jesus, it isn't true. Let's look at some examples about what God says about you and who you are to Him.
God loves you. The reason Jesus came is because He loves you (John 3:16, Romans 5:8). You are a new creation made with the nature of God (2 Cor. 5:18). You are accepted in the beloved (Ephesians 1:6). The word "accepted" here is translated from a Greek word that means highly favored. You are highly favored by God. In fact, His favor surrounds you like a shield (Psalm 5:12). No weapon formed against you shall prosper (Isaiah 54:17). God see's you as righteous and good. And this righteousness has nothing to do with your performance, but it has everything to do with your faith in Jesus Christ. (Romans 3:21-30). This righteousness status isn't for the people who do the most good things, or who avoid doing the most bad things, but for all who believe (Romans 3:22). Even if you feel guilty, God's truth is greater than your feelings (1 John 3:20). You are the righteousness of God in Christ (Romans3:22). God will hold nothing good back from you (Romans 8:32). You are not under law, but under grace (Romans 6:14). God loves you and wants to get personal with you. God wants you to know Him. Your body is a temple of His Holy Spirit (1 Cor. 6:19). He will never leave you or forsake you (Hebrews 13:5). You are a minister of reconciliation (2 Cor. 5:18). Jesus lives in you and expresses Himself through you. He loves you, and He gave Himself for you (Galatians 2:20). You are royalty. You are a child of light (1 Thess. 5:5). You are a child of God (1 John 3:1). You are one of God's precious gems. You are like Jesus (1 John 4:17) and His beauty radiates through you.
By all means, stand up for what is right. But don't feel like you need to come down to the level of arguing and defending yourself if someone doesn't agree or understand something. It's the Holy Spirit's job to help people believe. So tell people the truth and then let Him do His work. If something does need to be said, He will give you what to say. Don't be distracted from doing the right thing to stop and argue with someone. You know the truth. So be secure in your relationship with God. Why believe someone who didn't die for you over someone who did? Arguing is just a distraction. Believe what God says about you. You are valuable to Him.