Have you ever met a Christian and pondered what part of them was Christian?

Consider Breakthrough's block a blessing in disguise, for I'm blocked too, thus your Q is the only way I can offer an answer! Yes, the 'Christian part' of a person is invisible because it's spiritual - of the Spirit. All Christians are indwelt with the Holy Spirit but if they start to grieve the Holy Spirit (disobedience, bitterness etc) then His blessing does not continue and it can become obvious to observers that something is wrong with that person's Christian stance. Once they repent of that sin, they can be restored to full fellowship with the Holy Spirit. There's also the matter of new and 'weak' Christians who have a lot to learn and many unchristian habits to drop. These 'babies' in the faith are often targets for the ungodly, to mock them. And some, sadly, don't mature in the Christian faith, seeming content to remain spiritual babies. They don't 'grow' so their witness for Christ is only slight.

But a confusing problem is that many people who claim to be Christian have never become Christians in the first place! Those are the ones ungodly people love to point out and jeer at.  I mean, it's fairly obvious, isn't it? A professed Christian who lies, or who is living in an on-going state of sexual immorality, or who cheats on taxation, etc - what hypocrites! What disgrace they bring on the holy name of Jesus!

Let the mockers condemn, though. Jesus said that in the way we judge others, we will be judged, so they've got it coming to them - unless they repent.

Just kill your fücking self 

Jesus exists and is God. A person can know these things with certainty by way of having true devotion to the Immaculate Heart of the Virgin Mary.

Yes I have, and I had to wonder what caused the dichotomy between what they practiced, and what they preached. 

When the block they demonstrate their insecurity and your hitting too close to the mark.

The spiritual part. The part you can't see. We don't wear special robes, headgear, underwear (except Mormons). We don't have special curls or hairdos, wear armbands, lapel pins, get on our knees at sunset, drive horses and buggies, do anything visual that says, "Hey, look at me! I'm righteous!" The most we do is put a Jesus fish on our car or wear a cross under our shirts.

For crying out loud Breakthrough, unblock me. It's so much easier.