Here's where you lose the argument. There are specific texts created by the founders of Christianity (including the words of Jesus himself) which define what being a "TRUE" Christian is. THerefore, if it can be pointed out that one's actions are a contradiction to the tenets in these documents, it is very reasonable to say that person is not following the teachings of Christ. You are confusing Christianity (those who follow the teachings of Jesus and worship him as God) and Christendom, which is the Christian "Brand Name". Billions "wear" the latter, and I can't say how many are the former. By their actions you'll know them.