That is an interesting article. And I would agree with it to some extent. I have come across many Christians and churches who do acknowledge that we as Christians still sin like the rest of the world, the only difference is that we acknowledge that Jesus died on the cross for those sins and we engage in a life of repentance - turning away from that sin. We may fall, but we'll get back up and keep heading toward God.
However, as the article implies, there are many Christians who don't acknowledge to the rest of the world - or to other Christians - that they stumble, fall, sin, or make grievous mistakes against God from time to time. I do think that is part of the reason why Christianity can leave such a bad taste in some people's mouths. Everyone knows we all fall. But for Christians to turn around and claim they don't and not be honest about their shortcomings and 'wanderings', is simply a lie to those around them. We lose legitimacy as Christ's followers when we do that. And like the article said, we don't create an environment of honesty or openness.