One important thing to know about Christianity is that: It’s mostly not about looking after your fellow ones that claim to be Christ-like, it’s about what the Bible teaches you. And I think in this case: It’s about how well the Holy Spirit in you could expound the words to you. This is your assurance of salvation. Don’t be confused about how others (in Christianity) are living their lives, even though it’s enough to confuse you — Matthew 20:16, let your Bible be your validator.
Any characters you found in the lives of others should be validated against what Bible teaches us (mostly the words from Christ), if it doesn’t correlate, then stay away from it (and them!).
The one thing you can do is to call-to-attention the victim, and if your several efforts is futile, please let them be.
It shouldn’t surprise you that people that claim to be followers of Christ live absurd, Judas Iscariot; as much as he stayed with Jesus and listen to his words still had to betray him.
To me I think being a true Christian = Steadfast in the truth as the Bible teaches.