This is exactly why church (specifically inside individualistic American culture) can be so difficult. This is why relationships are hard to manage and why betrayal - or even relational cooling - is so common. The structure of modern church allows full membership to people who may not even know Christ and have any real agenda to know Him. Thus, John's words that true fellowship can only be experienced by fellow Christ followers should be a word of correction to us today.

1 John 1:3