MY BROTHER,
The "No True Scotsman Fallacy" does not apply when dealing with the appellation "Christian." Our Lord set out a very detailed description in Scripture of what a TRUE believer should look like--basically an image of Himself. He is the benchmark; He is the Measuring Stick; He is the Role Model.
Scripture states, "BY THEIR FRUITS YOU WILL KNOW THEM." (Matthew 7:20) So, it spite of the fact is has become a sneered-at cliche, "What Would Jesus Do" is an excellent tool for revealing the true identity of one calling himself a Christian. Ask yourself, "Would Jesus say of do this?" If the answer is no, then the so-called "christian" is a poseur.
Jesus never shunned anyone; never looked upon any of us sinners as "the devil's children", and He related to all--including those who were nailing Him to the Cross--and beloved children of His Abba.
"Christian" has a very precise definition, and it has NOTHING to do with how one spends their Sunday mornings--it has EVERYTHING to do with their manifestation of Christ-likeness. Read the Gospels; get a mental picture in your mind--and heart--of Who and What Jesus was, and use that as your point of reference as to who is and who isn't a "Christian." To paraphrase--"You can't judge of book by its title!"
(P.S. Don't go in the other direction and evaluate a person's Christ-likeness by momentary lapses. We are all a work in progress; we all have frequent lapses in our personal areas of personal weakness; and we are all people on the way. With a little patient observation, you will be able to spot the difference between who and what a person IS as opposed to the occasional aberrations and deviations which occur within that person--and ALL people, from time to time. "Bad hair days" are temporary glitches, not enduring character traits or, as A.A. puts it, "We are seeking progress, not perfection.")

ABBA'S FOOL,
ephraim