Huh, my Websters gives the definition as "one who professes belief in the teachings of Christ".
Key words there are "professes" and "teachings" to me.
Some people will profess to be Christian because of course, they believe it to be a good thing, and have one set of interpretations of the teachings of Christ.
Some other people will interpret the teachings of Christ, with equal conviction and sincerity, believing they are trying to be nice people, and also profess to be Christian.
Who decides which group is the true Christians, Christ? Why doesn't he just step in and settle it, or make it obvious in his words and book which of the hundreds of Christian sects is the "right" one, if there is indeed only one correct interpretation of Christ's teachings?
I dunno, I'm asking you.
Witnesses claim to be the "truth" based on a strict criteria of Biblical teachings too, and claim total purity. They claim to be the only ones who can correctly interpret the Bible for you, and that all the rest of Christianity is false if it even contains one element that is incorrect (the old "if a glass of water has one percent filth in it, would you drink it?" illustration comes to mind), but they themselves have been incorrect many times in the past, by their own admission.
That they get people to demonize other religions for being "false" when they themselves constantly update and change their own teachings and explain it away as not incorrectness or being wrong, but "increasing light" is merely proof of how good they are at mind control and damping down cognitive dissonance, that's all.
Those for whom it does not occur that their might be a reason different people interpret Christ differently and it was even intentional, well, isn't that a possibility?
Maybe there is no "one true" religion or one "right" interpretation of Christ's teachings as long as one lives by what they BELIEVE it to be, to the best of their ability.
As human beings with a natural diversity of thought and emotion, that may be the best we can do in interpreting Christ or anything, really.