Boy, have you hit the mole with the mallet.
"No True Scotsman" is extremely popular among the fundamentalists
Fact: Christians tortured and executed witches
Response: They weren't "True Christians"
Fact: Many Christians practiced slavery and used the Bible to justify it
Response: They weren't "True Christians."
Fact: Christians persecuted great thinkers like Galileo and Giordano Bruno.
Response:They weren't "True Christians"
And on and on it goes.
The amazing thing is that they really don't comprehend what is wrong with their argument.
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.