As Christians, the two things we can do to stand up for Christ are to live according to His Word and grow our own knowledge of Him. Christ said, “Let your light shine before men…” (Matthew 5:16). This means that we should live and act in a way that supports the gospel. We should also arm ourselves with knowledge, both of the gospel (Ephesians 6:10-17) and of the world around us. First Peter 3:15 says, “But in your hearts set apart Christ as Lord. Always be prepared to give an answer to everyone who asks you to give the reason for the hope that you have. But do this with gentleness and respect.” All we can do is live and teach as Christ would and let Him take care of the rest.
Critics of Christianity have become more vocal recently. This is partly because there are many people who do not believe in God or understand the truth about Him at all. Yet the apparent increase of anti-Christians is also due to perception. As with many topics, those who truly despise Christianity are the loudest and most vocal of the non-believers. The vast majority of those who do not believe don’t care enough to bother believers. The few angry, vocal, bitter unbelievers make enough noise to seem more numerous than they are.
Read more: http://www.gotquestions.org/anti-Christian.html