Such a statement demonstrates not only a deficient understanding of the nature of Church, but a misunderstanding of sin.
The Church cannot sin because her divine elements prevent this. Men who choose to reject the teaching of Jesus do sin, and in doing so, separate themselves from His Holy Bride, the Church.
In fact, there is quite a bit of evidence that Jesus intended to keep His promises to prevent any sin in His Church. He promised to lead her into all Truth, and that the gates of hell would not prevail. There is no quicker way to pass through the gates of hell than sin.
I have never denied that men within the Church sin. We see this clearly in the NT. Ananias and Sapphira are a good demonstration of what happens to people in the church that try to lie to the HS.
There is a visible church left, in spite of centuries of ravaging and corruption from sinners. The reason that the visible Church is still standing is because she is infallible, and of divine institution.
It is certainly a great wound to the Church when persons occupying official capacity choose to separate themselves from her through sinful actions. However, they do not represent the church in their corruption any more than Judas represents Christ in his betrayal. That is like saying that all of what Jesus taught is defunct because Judas acted faithlessly.