It was the Apostle Paul who said that bad company corrupts good character (1 Cor 15:33).
You could make the case that that's what happened with Robert Robinson. The British Pastor from the 1700's was most famous for writing the hymn Come Thou Fount of Every Blessing. Unfortunately, he had a close friend, Joseph Priestley, who was a Unitarian and many accuse him of influencing Robinson away from God.
Haven't you seen this pan out before in your life? A family member or a friend appears to be following Jesus, but one person, one bad apple seems to spoil them.
The Bible warns us that in the end there will be scoffers, there will be people who call themselves Christians, but choose to follow ungodly desires instead. And it's for this reason that the Book of Jude ends by reminding you to hold fast to God. "To him who is able to keep you from stumbling and to present you before his glorious presence without fault..." (Jude 24).
In other words, despite how our culture is perverting other Christians you know, despite how political correctness is trying to seep into our churches, you can remain strong in Christ because He is able to keep you from falling. Don't cave.