Here is how various interpretations of the verse you chose (1 Corinthians 6) deal with the word that in your preferred version is rendered "fornicators"

NLT: "those who indulge in sexual sin"
NASB: "fornicators"
The Message: "...those who...use and abuse sex"
NIV: "sexually immoral"
KJV: "fornicators"
AMP: "adulterers"
CEB: "those who are sexually immoral"
The Voice: "those whose lives are defined by sexual immorality"

Someone reading that verse in a bible version other than the one you read it in might reach a different conclusion from you. The reason is that it's not as clear cut as you would make it out to be. The word used is "pornoi" and it does not directly translate to fornicator. The best direct translation would be "male prostitute". But given the context wherein it is used, I tend to agree with the way that "The Message" and "The Voice" translations phrase it.

It's quite possible you are right and the intended meaning is "fornicator" (although it would be difficult to defend that position given the lack of evidence). But the point isn't whether you are right or not. The point is that there are alternate views different from your own that a Christian might have. A Christian who reads the NIV version (which is the second most popular protestant version) would not have reached the conclusion you did from that verse.

Sure, there are other verses you could point to. But the same thing would occur. The point is that your interpretation of what the bible says is not the only one and it is wrong of you to assume that yours is so far superior to everyone else's that you cannot call anyone else a Christian unless they agree with you on that point. You sound a lot like a pharisee.